He can’t make me cum

So me and my boyfriend have been having sex for nearly two years now and no matter how many times he goes down on me or fingers me he can’t make me cum. Sometimes it’s because he asks if I’m close which puts me off completely and stops it for me. Another reason it happens is because me and him often smoke weed together which makes it harder for me to cum but even sober i still can’t do it. I’ve faked it so many times because he goes for so long and I just know it’s not going to happen. The only time I can cum is when I’m on my own. I don’t really know what to do as I don’t want to hurt his feelings but can anyone give me any tips? I saw online someone said to just relax but that’s not really helpful. Does this happen to anyone else? :( xx