Hello all! How do i get over this fear? Do i have a disorder

Hello all. I begin liking this forum as i saw quite amount of meaninful posts and im new here. I'm a 20 year old guy right now. I started to get paranoid and uncomfortable when i'm doing something which can be seen even in my room with the curtains opened. I only feel comfortable when the curtains are closed. I have a fear of people from the opposite watching me through the windows. I don't know it is true or not. It might be irrational but i can't get rid of the feeling and I'm afraid to look at them fearing what i think was true. When I'm out alone having a drink and facing a flat with a lot of windows, I would feel extremely scared and thinking that someone is looking at me and judging me. If i saw someone there, i would be thinking that they are looking at me. My mind is telling me that they might be thinking that i'm watching them. This all started after dropping out of school. I started to recalled the negative things i did in the past. When i'm a young boy at the age of 12. I masturbated looking at my elder sister in a room without her knowing which is wrong. After that i stopped and doesn't have the urges because it is wrong. I felt extremely guilty and remorseful about what I did in the past and started to be paranoid thinking what if other people from the windows saw what i did? I'm having a hard time doing my things now with the curtains opened and it is making me sad everyday? Any kind advices thanks?

Welcome to the forum. I don't know much about paranoia, though there is a forum for paranoid-personality/ disorder which might be interesting to you. It can come about as an aspect of many other issues, though, so please don't diagnose a personality disorder straight away! Are you able to see a therapist at all? I think talking it through with a professional might be the most helpful approach.