GF is bigger than me

New relationship for 3 months and I’m starting to realize I feel weird about my own body compared to my gfs. So we have a closet with mirrors in front of the bed and I caught a glimpse of myself being fucked last night and I had never realized how small I am compared to her. I don’t know why it made me feel weird. Does anyone else have this issue? I am so attracted to her, it’s just that I was a bit shocked at the difference. She’s 6’2” and I’m 5’3”. Sometimes sex feels like we have to spend a bit more time figuring out how we can position ourselves so that everyone feels pleasure and not pain. Idk, I’ve just never even thought of body differences and now I realize my new relationship gets me nervous?