 During masturbation I imagine my ex-girlfriend having sex with another man. I don't know if this is normal but it's making me feel very guilty. Honestly from all the messages that I receive I can tell you that 90% of all people regardless of gender will fantasize about their ex during masturbation. You see when you masturbate you need to create a story in your head. I guess that's why so many people watch porn while masturbating because the story is already there. But if you are not watching porn while masturbating you have to create your own story. Most people will either go back to something that they enjoyed in the past or at least partially something that they're familiar with. Your ex is most likely going to feature in it. And so to answer your question one yes it is very normal almost everybody tends to do this so don't feel guilty about it. Two you wanted to know how to get rid of this fantasy. This fantasy will run its course at some point. Every fantasy stops being exciting after a while. Just wait for it to pass out of your life. And finally if you're still feeling guilty just think of this fantasy almost like a sex toy which comes out for a specific time or specific purpose and when you're done with it it gets washed, cleaned and put away till you are ready to use it again. Honestly this does not have any more space in your life than simply a useful tool.