This helped me. I saw it advertised as something dumb and I immediately went to buy it.
HOMCA Memory Foam Pillow for Couples, Adjustable Cube Cuddle Pillow Anti Pressure Arm Pillow for Back Sleepeer and Side Sleepers https://www.amazon.com/dp/B08D7MN1MQ/ref=cm_sw_r_cp_api_glt_fabc_BMN60YSNNJXNE1ZKQ9HP?_encoding=UTF8&psc=1
They actually make special cuddling pillows with a slot for your arm
HOMCA Memory Foam Pillow for Couples, Adjustable Cube Cuddle Pillow Anti Pressure Arm Pillow for Back Sleepeer and Side Sleepers https://www.amazon.com/dp/B08D7MN1MQ/ref=cm_sw_r_apan_glt_fabc_KZKVERG6MY3VYA6HDK76
Another interesting pillow