That's me 2 months ago (im 6 months now too)~ As I'm short and petite, my belly looks larger than normal and it's very uncomfortable to sleep! No matter what position I sleep in, it isn't comfortable, stomach is too heavy and stretched if I lay on either side but I can't sleep on my back either. So I took lots of pillows and stacked them behind so I can sleep sitting up. (like 45 degrees) I find this the most comfortable position which I can stay for the longest period of time. Try to experiment which is the most comfortable position for you, (sometimes you might like a harder bed-maybe your sofa, or a rougher bedsheets, or just a bolster between your legs can relieve quite a bit)
Also I find wearing pregnancy dresses isn't as comfortable as just wearing normal skirt or loose pants where it will slightly "carry" your tummy so it won't be as tight. If it gets too tight, maybe you can get a pregnancy belt, the one which can sling onto your shoulders. Maybe also check if it's your bra that is too tight. I find that getting a looser bra actually helps a lot.
Read more