Vent/advice pls..

Ladies, this may be long so if you take the time to read this I want to start off by thank you.

For the last 2 years, I’ve been battling with mental health issues. I’ve been seeing a therapist, but she was no good. I tried medication but it wasn’t working well with me. I noticed that I tend to make my life a living hell, when in fact, nothing around me is bad. Actually, my life is pretty great. I’m a full time college student, engaged and have a house with my fiancé etc. I noticed that I sit here and make everything extremely negative and cause problems out of thin air. My fiancé will ask if our friends could stop by to hang for a little bit and a switch will turn in my head and I’ll feel mad. I’ll start coming up with reasons why they shouldn’t come and put my fiancé down. I noticed sometimes hell have them come anyways because of how irrational I am, and they notice my mood too. I’m fully aware my actions are irrational and toxic but for some reason I can’t work towards fixing it. I am bringing him down big time and I think if I don’t fix this soon, he may leave me for his own mental health. I’m scared Bc I feel very alone and can’t explain how I am feeling but I just want to be happy and positive 😔 please someone