Mattress topper?!

My bf's bed is so uncomfortable. I could actually cry lol, going from my pillow top mattress over to his hard, springy bed is actually the WORST. And mattresses are super expensive, I have a fluffy mattress topper but it gets flat and is basically useless. This is no way for a 6 months pregnant girl to sleep 😭 does anyone have a mattress topper they love or know of any good inexpensive ones??