We have been fighting a lot lately, she was talking to her ex husband and flirting with guys and I caught her, then I became just a monster... Very upset and spying and accusing her of stuff literally almost insane lol
It's a hard situation. You didn't act in the best way and it weighs on you. I don't know, maybe you need time to forgive yourself, and some action from her that you don't ask that reassures her love and commitment
Being so resolute will probably reduce the chances of finding a happy relationship. We must give people space to grow, feel, doubt, question, and we must stand by them, reassure them, love them. And they should do the same to us.
Maybe going for walks or a drive alone helps, as well as writing it down. Think about each action that you did and what led you to them. Recognise that how you felt is valid. Rationalize how you could act correctly next time. Then rationalize what you expect from your fiancee, and accept that she's still learning how you are, what hurts you and what makes you happy. Talk with her, be honest. And a relationship requires both people to make an effort; you should be flexible and understanding with her, but verify if the relationship is making you happy and improving your life