Faint cramps while laying down.

Melanie • TTC #2 off & on for 5 yrs.This year is the 1st year of tracking cycles & got pregnant 2x this year. I miscarried w/both.
When I lay on my back, that is when I can feel faint cramps on both my left and right side of my pelvic. I can also feel light back pain. But when I stand I don't feel anything. Has this happened to anyone else? It's so weird.