Ejaculation problem serious question

Ok heres the deal, I'm 23, in the past 7 years I've had 2 different girl friends. I am not currently with either of them but still see and have with both. With girl A she has a tight and with girl B she is a little looser. Both have told me I am the biggest guy they have been with, I'm not saying I'm huge but outta 30 guys I'm the biggest. Any way with girl A I within a minute, but with girl B I can go as long as I want. So I'm guessing I faster with girl A because there is such a snug fit, what can I do to last longer? or maybe there are other answers to what the problem would be? I open to suggestions here