i feel fine lying on my back at 32 weeks

there may be times where she will shift in a position that causes discomfort and shortness of breath but 95% of the time when i lay on my back i feel completely fine and she keeps moving with no problem. i'd been expecting to not be able to lay on my back since 20 weeks so it's kind of weird. i am carrying very small for how late in the pregnancy i am but i dont think that would even be a factor because the baby and my uterus are measuring normal (baby is actually over 5 pounds already 😳) anyone else experience this?