Feeling unwanted and lost

My boyfriend and I have been together for over five years. I'm 32 and he's 25. When we first got together we cannot keep her hands off each other and had sex daily.  Now I know the honeymoon. Doesn't last forever and it varies from relationship to relationship, but over the past year our sex life has dwindled significantly. We might have sex once a month, and as of right now it's been a month and one week since we last had sex. He has always enjoyed getting blowjobs though, and I always get him off, but last night I decided to be spontaneous and give him a BJ because he is been working so hard and stressed out. I noticed after a few minutes that he wasn't really into it, so I gave it my all, and after about 10 minutes he said he probably was not going to get off and I stopped.  This has never happened before; he always gets off! I have been feeling very unattractive and unwanted lately because of this.  Anytime that I have tried to talk to him about our sex life and how I feel like we have lost our intimacy and connection, it usually turns into a fight and he says that relationships are not all about sex, which I agree, but it is a very important part, especially since we used to have it. How can you be in a relationship with someone that you do not desire? He's 25 years old for Christ sakes! If I can't even talk to him about it then what the hell am I supposed to do!?