I have read if someone is sleeping with someone else their sexual needs may change. I mean, trying things with you that are out of the ordinary and wanting more love making.
What about when a complete reverse happens? What used to “last longer” can’t seemed to be controled to prolong love making and is over in a matter of 30 seconds. I have found that if a man is “getting” it regularly, he can last longer before orgasm. When he is not getting his needs met he has a orgasm fast and his performance can’t go longer.
My suggestion is that you not “assume” that because a partner’s “staying” power before finishes changes that he is now sleeping with someone else. PLEASE, PLEASE don’t try to “analyze” the situation from something that you heard.
Most of such “stories” are not correct.
About 30% of males have what is know as “rapid orgasms” or “cuming too quickly”. That means that they orgasm before they want to. In the case you describe, where the fellow used to “last long”, and now can’t control when he orgasm may just be a matter that his genital (and brain) have “learned” how incredible the sensations will be from your vagina.
That “programed” genital/brain combination now just reacts much much faster than it did originally. That of course is only one of several possibilities. AND yes, maybe he just need your lovin’ more often. PLEASE don’t assume that from his lack of control he is now sleeping with another.
What he needs is your support and understanding, not accusations.