No longer excited to have sex with husband.

I'm having a hard time getting wet and excited. I get turned off by trying to rub his soft penis because it is so small when soft. It seems to be no bigger than my thumb when it is soft but it does grow into about 5 inches when it is hard. He also can't do some  positions due to him not being long enough. I don't get very excited being on top because I can't ride up and down like I could with men who are bigger. We hardly have sex because I don't look forward to it because it ends up being disappointing. It is also a lot more work with him. Ugh I feel sexually deprived. I feel like our marriage is going to fail over this issue. I don't know how to get over this issue.