Anyone else have this problem?? So annoyed..

So my SO & I had sex earlier today for the first time in like 3 days. Well he's 20 and I'm 18. We've been together for around 5 years..But he never want to have sex, He gets hard and everything but says he's not horny. So today I begged him for a good hour and finally got him talked into it and honestly it was no longer than 15 sec. no joke. I was like "really" and he said it wasent his fault and went to sleep.. I'm so annoyed with this.  It happens all the time and I try to talk to him about it and nothing helps. Has anyone been through anything similar