Finishes too fast

So me and my boyfriend have been dating for almost 5 years. We are 21 and 22. The first year we never had a problem with how long our sex lasted (sometimes up to 1 hour) but after the first year it doesn’t last longer than maybe 5 minutes if even that… I’ve tried talking to him and he gets upset and says he can’t do anything about it, then he gets his feeling hurt. We go weeks without sex ( the longest a month) then there’s some weeks where we do it every day but it’s always the same thing. I don’t know what to do anymore because I’m never satisfied. I need help!