Failed oral sex tonight

So my boyfriend wanted me to give him head I suggested I get on top of him reverse so he can eat me out and while I was on top giving him head 5 mins in it he was like I can’t breathe.... we haven’t did “69” in almost 3 years and during the 3 years of being with him we only did it like 3-4 time I gained over 100lbs he gained 40 lbs in the 3 yrs we been together and I’m the heaviest on and kinda hurt my feelings that I can’t satisfied him if I’m on top of him... so I need advice on losing 79 lbs. no rude comments