Is wanting sex more often bad?

I am a 33 year old mom of 3. My fiance is 26, with no kids. We have been together for just over 3 years. In that time, he has repeatedly told me my desire for sex is a problem, mind you, we have sex maybe a couple times a month!! I tell him I'd like to at least be intimate a couple times a week and he gets upset and says I'm never satisfied!!! I am completely satisfied when we DO have sex, but its hardly ever... Any ideas on why he's like that or what I can do. (Ps no he's not cheating, and yes, I'm sure)