If you really wanted to leave him and separate you wouldn’t be worried about doing so and it wouldn’t make you as destrort as it seems to be from what you have written. Having what if thoughts usually indicates ocd but obviously only a professional can say for sure!! “What ifs” almost never happen and in my experience have never happened!!!! Not one of my ocd thoughts have ever been real or happened and the more you fixate on this the more it will take over your life - ocd is the doubting disease and makes you doubt even the simplest things!! And even if this wasn’t ocd you wouldn’t be a terrible person for having thoughts - they are just thoughts.
If you don’t want to leave him and you are happy with him then it is probably ocd and you should go and see a doctor because ocd starts off as one thing and spirals into another most of the time - it’s a horrible thing which makes you not trust yourself and you should.
I hope this helps.