This is a serious post, I'm not trolling and really want some advice.

I'm a 25 year old guy and ive had a stunning girl that I love for almost 9 months now. Things are going great, except the fact that I get intruding thoughts about other guys looking at her/touching her/doing sexual stuff, and then I get paranoid that she wants it too. It started off with some dirty talk like calling her slut in bed, then to asking questions (e.g you like guys looking at you don't you??) to full blown saying disgusting shit like 'i want you to blow another guy while I fuck you'.

As soon as the sex is done I feel fucking disgusted and literally despise myself. What the fuck is wrong with me, how can I fix this? My girlfriend has never given me any indication that she likes it or is into it, and has never said yes or joined in to the stupid shit I say, even arguing with me about it.

Is this an insecurity thing or something? How common is this? Please, if anyone has any genuine advice or has got over this shit themselves I'd really appreciate some help because I'm gonna lose my mind if these thoughts and desires keep coming into my head