ok ladies I need help! 😪

Ok, so I've been with my man for 12 years. And recently the last two times we had sex it's been different. He gets hard and stays that way for a while but then when we keep going he all of a sudden gets soft. And it takes him awhile to get him hard again. And then he gets soft again. I asked him if it was me if he wasn't attractive to me or am I doing something wrong. The last time he told me he ready if a man works out a lot his stamina is longer. But then when I asked him again the next time he th to blame it on me saying that my vagina feels different. Like iven been cheating or something😓 this really hurts me that he would even say that because IVE NEVER CHEATED ON HIM. so for him to say that really really hurts. Please ladies help me and give me some advice. What am I doing wrong.Â