Sex issues

Have any of you run across this problem? If so how do you fix it? my husband and I have been married for almost two years. He's 8 years older than me. We haven't been having sex maybe once a week sometimes once every two weeks sometimes longer than that. When we do have sex he finishes to soon and I'm left frustrated. I can't tell you how long it's been since I've had an orgasm. I've talked with him about this, how unfair I feel it is that he withholds and then when he does give in he doesn't wait for me. He said he knows its an issue and knows how it feels to be on my side, because his exwife did the same to him. He says its not intentional and he'll try to work on it. But the very thing we talked about happened again. Am I being selfish? I've always aimed to be a Proverbs 31 wife, and I feel guilty because I want to have sex more than him, and that I feel anger towards him or disappointment when he doesn't wait on me. I've already brought this up with him and we talked but it's still happeniI don't know what to do anymore. Am I being selfish? Is this my problem I need to fix? If so how?