I think I do have a kind of powerful sexual attraction towards my friend. It goes on and on since years, since 2022-2023 I'd say. It was the strongest in 2023. I cut contacts with her because i was afraid i might cheat on my girlfriend back then with her. I was so attracted to her that it was crazy. And i did some mistakes in relation to her which fueled it back in the day, the problem was that i delved into a conversation with her back then, in which we shared our sexual and relationship views and they were matching alot. She was chubby too, and she was kind of my "perfect body idea", and I negated my attractiveness towards chubby girls for years and then it exploded into her [my partner is chubby too, and very attractive for me, its even more crazy!]. I avoid her, i silenced her social media, and im satisfied in my relationship, yet this shit goes back to me, to my head, makes me questioning myself, my sexuality, my own mental health sake and "what-ifs" are killing me. It goes back, since years, even though I thought the worst is long behind me. Any advice? Do I need a therapy?

man just go to therapy

You want what you can't have. Man up.