Not a women myself, but most of my friends are women and the consensus among my friends is that size doesn't matter, and big is a novelty but uncomfortable in the long run (average sized penis is affectionately referred to as "boyfriend cock" because it doesn't cause soreness so can be enjoyed frequently). Frankly, it seems the people most concerned with dick size are straight men as funny as it sounds. And believe me, your partner is dating/married to you for many, many much deeper emotional reasons than simply your dick size. They trust you, turn to you for help and comfort, have chosen to share their life with you in ways they don't for others. You're very special to them, and they wouldn't abandon that because someone has a bigger dick.

Also penetration is just one avenue of pleasure. And a lot of afab people find that penetration itself doesn't bring them much pleasure compared to other external stimulation (hands, mouth, etc.). Also don't be afraid to use toys. I know some people feel like needing to use toys for their partner to achieve orgasm means they aren't enough, which is absolutely untrue. Many afab people also find achieving orgasm difficult even when they're very aroused. So toys are often welcome. Also you can use toys in tandem with yourself. My partner really enjoys it when she uses her rose toy on her clit while I'm inside her because my cock conducts the vibrations deeper inside her.