My ex husband his thoughts in my mind?

I married a guy who rather we dovorced 3 months after marriage for reasons that i am not very clear Now what has happend is that I married another guy after that Though we are happy and have regular sex the problem is that whenever we have sex I think of my first husband as I feel he was much better in sex than this guy How do I overcome this feeling how do I get this guy out of my mind There are any medications or treatment for this ? Please advice me I will be very greatful if some oen cna help me out in this istuation sir