It might be different for your friend, but when I first started to tell my closest friends that I was ace, I had a very good idea of who I am, and that the only thing I wanted was to let them know. And that they made me feel safe and they would be cool with it.
It kinda seems like your friend is doubting himself, so if he is comfortable telling you that, I think you are well on your way of supporting him. And I think it means that you are a very good friend to him.
I think I would either let them talk about their experiences very broadly and open-ended. It can be as easy as talking about people he like a lot, and why he likes them. Questioning yourself can come from very random places. Like my friend said he was upset that he couldn't have sex, and I just couldn't wrap my head around that, and after a while I stumbled upon asexuality and everything clicked.
If he doesn't want to talk about himself, you could also perhaps talk about your experiences. It is kinda difficult knowing how you are not feeling a certain feeling. Somebody talking about how they are attracted to other people always reassure myself that I don't feel any of it.
How does your friend like to learn things? For me it helped reading a lot of books. I would recommend, Ace: The invisible orientation. That book I think also have a chapter for supporting aces, so it could be beneficial for the both of you.
I'm really repulsed, so I hate everything with the topic sex in it, other people around me talking about are really cringe to me and so does the TV series or films with sex scenes in it, I'm always skipping them
But I wanted to be really sure about it that I'm asexual so I had a phase where it was even for me very hard to understand, but I can recommend you this book I've also read, it really helped me to know about more about myself
https://www.amazon.de/dp/1634502434/ref=cm_sw_r_cp_apa_glt_i_AJQ6NF24FGH2TTDDSA72
Give him a book or two back:
And sit him down to discuss with him, minus the wife, how much his decision to give you a book that makes assumptions about you and your happiness really hurt you. Tell him you understand he did this because he cares for you and religion features heavily for him but in giving the book it showed how much he fundamentally didn't understand or want to understand you and your perspective. You are thus giving him a few books so he can understand you better and ask that he respects you enough to not make assumptions about you in such a way again.
Hi OP, I have read through or skimmed the comments and your replies, so I will not mention birth control, stress, anxiety, trauma, or porn. Except that I just did... sorry about that.
A few things come to mind, mostly long shots though, and no spectacular insights.
Getting the boyfriend out of the way, his comments are dismissive and unhelpful, but probably coming from a place of ignorance rather than malice. It sounds as though the problems predate any of his involvement though, so I would assume they are not relevant at this point.
First real point, you mention frequent masturbation with and without toys. In some women that can lead to an adaptation of the nerves around the clitoris and vagina because the sensations are more concentrated and intense, and the body comes to expect that as the threshold for pleasure/orgasm. Effectively, sex is not stimulating enough. However, you also say that your toys no longer work. I assume that what you mean is that you can feel the vibrations that would normally give you pleasure, but none of the usual stuff works, is that correct? Hitting the g-spot, for example, would normally be wonderful but now it just feels like vibration and not at all stimulating?
Second, asexuality is something that can come at any time, and there is not really a test for it nor is there a single route to arriving at asexuality. Some studies also suggest it is not so much a disorder to be diagnosed and cured, but an orientation. Sometimes, the expectation of fantastic sex and an appetite for masturbation, can lead to a "huh, was that it?" reaction following the first sexual experience, and there you are. The hard part about it is that sexuality is a spectrum, and asexuality is not just a single point on that spectrum, so different asexual people present in different ways. Others have suggested some good books ("Come as you are" is a good one), but for something specifically about asexuality I would recommend "he Invisible Orientation", which worked well for my girlfriend.
https://www.amazon.com/Invisible-Orientation-Introduction-Asexuality-Generation/dp/1634502434
But before buying anything, check out some of the basic info about the topic and see if it resonates:
https://www.healthline.com/health/what-is-asexual
https://www.psychologytoday.com/us/blog/the-invisible-orientation/201503/asexuality-is-not-diagnosis
Third, how attractive do you find your boyfriend? (A sensitive and incendiary question, I know)
Are there any other individuals out there that you find attractive? Or any "types" of people? I am not suggesting that you go out and be unfaithful, have sex with other men, women or others, all in the name of identifying the issue. But exploring the problem from another angle can sometimes help... if not to answer the problem, then at least to eliminate some incorrect answers.
Fourth, how is your thyroid? (It is a small gland in the throat, just above the top of the sternum, and even some doctors do not know much about it, so you may need to ask for a referral to a specialist)
If your normal doctor is amenable to running some blood tests, ask them to do a Thyroid function test, and hormonal test for the T3 (Triiodothyronine), T4 (Thyroxine) and TSH hormones. The normal and optimal level ranges vary markedly throughout life, and when we have infections, tiredness, and stress. In short, the pituitary gland produces TSH, which stimulates the thyroid gland to produce T4, some of which will be converted to T3 in your body. High TSH and low T4 levels suggest hypothyroidism (an under-functioning thyroid), while there are also potential diagnoses based on your T3 level.
The reason for asking about the thyroid is that one of the more common symptoms of hypothyroidism is a reduced or completely absent sex drive. Ironically, having slammed your bf for his comments, some hypothyroidism diagnoses are best handled with lifestyle changes rather than medication (working out, and dietary changes), so rather than being insensitive, he might be a genius!
Lastly (ok not last exactly, I can go on and on, but I am sure you have better thngs to do than read what I am writing), has your gyn ruled out early-onset menopause?
here's a book: https://www.amazon.com/Invisible-Orientation-Introduction-Asexuality-Generation/dp/1634502434
and a playlist: https://www.youtube.com/playlist?list=PLMKCk6HaXC8-X1N3gA5QN76ED4yn_6t2d
we also like cakes and garlic bread