Sex loft changing

So my boyfriend and I have been together for close to 5 years. Were bout 24, have a dog and are in a happy solid place. Our Sex has always been amazing, and I am not shaming him in any way but it has changed.

The sex is still amazing, he still feels amazing, but our sex has gone from lasting a long time (30 min) to 10-15 (still long) 3-5 minutes, 1-3 times a week, and now we barely have sex ( 1 time every month or so) and when we do it only lasts, and I kid you not, 3-10 seconds). He feels bad, I get frustrated but don’t want to make him feel bad... I don’t know what to do. I love him it doesn’t change that, but I miss our sex life.