Is thinking about your ex while you’re with your present considered as being unfaithful?

i think you should speak with Your Ex.By the sounds of it she doesn't seem very happy in this relationship and it looks like you both still have feelings for each other am i right? but anyway if your ex doesn't love/like the guy she goes out with there isn't a point to be honest with you.But for now don't interfere with their relationship,if they brake up they brake up.if they don't and their happy together then leave them be

It's not unfaithful, it is actually a normal thing, you tend to compare to something you know or experienced to see if it's better or worse and relationships tend to have a simmilar trend of events so it is unevitable that you compare it to the past and even more if it was important to the person. If it's worse then she will probably think that she was better with you and that is what it causes the problem because then she tells him and then he feels inferior and etc . My advice is let it be, just tell her that she should be happy with her new partner and if that is not the case she should move on.