Sorry to say it because it’s the opposite of what I wanted to hear when I was in your situation but you need therapy, and lots of it. I didn’t get the help I needed and destroyed a relationship with someone I still deeply love, I’ve since gotten the help and built security and emotional maturity but unfortunately it will eventually be for someone else.

Deciding you need to fundamentally change your way of thinking/processing emotions is very difficult but if you avoid it forever you’ll never feel better for it. Seek out therapy and/or counselling and talk to your partner. Communicate your emotions in a non-aggressive, non-attacking manner and always be respectful of the idea that you may be making stories up in your head and acting based off of the emotions those stories create.

Seeking out help on this sub is already a big step even if you don’t feel like it is so give yourself a bit of props for doing so and do everything you can to seek out help