Sex Positions

When TTC is it important to try different positions? My husband has severe back issues and so the only position we ever have sex in is missionary. I don’t complain though because it works, but I’m just curious as to what everyone else thinks. My best friend is convinced that she got pregnant by being on top, but I’m a bigger girl and I just don’t feel comfortable doing that. What are some ways I can boost my confidence enough to try new things? Thank you in advance! 😊😊😊