She threatens to break up all the time

I have been struggling with trying to convince my girlfriend that I’m not cheating on her. She has no reason to doubt me, and I don’t even talk to other women because I know how possessive she is, but this doesn’t help in any way. We have been in a relationship for two years and she threatens to break up whenever we have an argument because she thinks I want to be with someone else. If I didn’t love her, I would have ended this a long time ago because of how stressful it is. I spend days trying to get her to believe me and it’s exhausting. I don’t know how much longer I can keep this up. Should I assume there is no hope for us if she can’t change her attitude?
Yes, you can assume there is no hope because no relationship can survive without trust, and two years of not being able to build that is definitely a bad sign. She may have reasons for being possessive, but they don’t matter if there is no effort made to understand where you’re coming from, or what this is doing to your mental health. Love is sometimes not enough to sustain a relationship, and you may have to evaluate what you are giving up in order to be with her. There’s nothing healthy about being possessive if it starts to stifle the person you’re in a relationship with. Try telling her that and if it makes no difference, you should think about when your love will start to curdle into resentment. It may be better to make a decision about your future before you get to that stage of anger.

My boyfriend doesn’t support my passion for beauty products, and I don’t know if I am being unreasonable by insisting on spending money on them. Is he right?
If it’s your money, you have every right to do what you want to with it. It’s also important to try and see things from his perspective though.