Hi and welcome to the forums!
I used to struggle with this quite a bit, not just with my partner but with my friendships. In fact on occasion I still do to a lesser extent.
My last episode where I was going through these feelings, I got connected with a counsellor at my university (as I could not afford to see anyone else) and I felt that really helped. It was nice to talk about the things that were bothering me with an unbiased person who could help me to remember the positive attributes of that person and why we were so close. It also helped me to build the confidence to confront them with the issues I had with them rather than bottling them up in fear of rejection. It really helped. I think seeking a mental assessment will definitely help, as they can help you connect to these services.
i wish you best of luck!
