Just because he came doesn't mean he had a great time. Guys ejaculate in their sleep. Have sex again and see how it goes. Generally, the more you get to know a person sexually, the more interesting the sex becomes. The second option is to deal with it and be thankful that you have a loving relationship.
Great sex involves more than just a big penis.
I understand that you'd like him to have a larger penis, but that won't always be the answer to your problems. A good relationship can make up for lackluster sex, but good sex cannot save a bad relationship. There's also more to sex than penile-vaginal penetration. Try concentrating on the other areas of sex. The third option is to dump him and move on to someone else.