Does it mean something if a person's attitude changes after sex!?

Answer 1

It depends on how long you waited before you had sex. If you had sex before you had time to formulate a proper and equal loving relationship, then it could very well ruin what you could have had. The problem here is that you didn't say whether the person's attitude changed for the better or not. If not, then he is the wrong guy, and was only in it for the sex. If for the better, then you are on your way to having a beautiful time together. Good Luck!

Answer 2

It means they got what they wanted and aren't interested anymore.