Prerequisite for sex?!!

Hello ladies. I'm 31 and my bf is 40. We have been involved for 2.5 years. Dating for almost a year. The last few months put sex life has been dwindling and I dont understand why. It went from 4 time a week to maybe 1. I've asked all the questions and I know he isnt cheating. 100 percent. He just says "I dont know. Just not in the mood." Now this is gonna get TMI. For those of you like me who are always curious here it comes. So it resolved and everything was fine. But then its like foreplay went out the window. Why do men think women are good to go when they get a boner? I always attempt something to help assure the mood is there. But the moment hes hard enough he just boom inside and done. Now because there is no foreplay I might MIGHT come once. Then he is done and that's it. He used to love going down on me. Hes the best I've ever had at it. Now he just barely does it. I've asked if there was something with me. Or something off I should know about and he says no. Then when I ask why he doesnt go down on me or at least use his hand to help get me ready I get told "it's not a prerequisite for sex"??? I'm sorry.. I thought these were things that always happened unless they're quickies. I'm so fed up. So I go home and masturbate to make sure I'm satisfied. He then gets upset that I do that as he feels like he isn't good enough for me. I'm just frustrated. I've mentioned more than a few times why and he still just doesnt get it. Never mind we only have sex pretty well when he wants it. Not me.

Before we get anyone saying leave him or break up with him or anything along those lines... we are adults and relationships arent games. We are both very happy and committed but the sex has been seriously dwindling. I'm done trying to initiate. I'll just be taking Care of myself from now on. He can do the same until he sees a pattern.. any ladies here have any men who just dont see a reason for foreplay????