I’m a die hard back sleeper, I would rather sleep sitting up than on my side! I use this memory foam wedge and I believe it’s at enough of an angle to be safe and not put that pressure on the vena cava. I even use a pillow on top of it. Wedge pillow
So my five month old son and i have been cosleeping since leaving the hospital (our hospitals forbid cosleeping due to possible danger from mom being medicated among other reasons). I distinctly remember this stage you’re referencing. I have two life saving tips that helped me get through when my husband went back to work. 1) leg peddling exercises for babies! Here is a youtube link. I did these after every feeding all day and all night. My son eagerly lifted his legs for me to peddle and press out gas when he caught on. Bonus, by about 3 months he was pulling his legs up to pass gas on his own. Maybe normal development but i took credit for him learning that. 😂
2) this wedge pillow from amazon saved my hips (side lying is a valuable way to breastfeed but hurts my pelvis…on that note its a good position for baby to pass gas while feeding) and i could sleep safely with him at my breast so those constant feedings didn’t really wake us. For those few weeks he wouldn’t sleep unless in my arms. It definitely is a normal, exhausting, temporary stage.
Kӧlbs Bed Wedge Pillow with... https://www.amazon.com/dp/B082XK5QN9?ref=ppx_pop_mob_ap_share
If a pillow is useful, try something like this
I found this wedged pillow to be more comfortable than expected. If you want to buy: https://www.amazon.com/gp/product/B082XK5QN9/ref=ppx_yo_dt_b_asin_title_o06_s01?ie=UTF8&th=1