impulsive thoughts of my bf cheating

I’m at a loss about what to do. I’ve been with my partner for about a year. I’ve wanted to be with him for 3 years and now I finally have him, I got out of a really toxic 11 year relationship about 4 years ago so I’ve had plenty of time to heal, things where going so great at first in our relationship and I’m still very much happy with him, I love him more than anything, but the past 5 6 months I’ve been having a constant fear that he’s gonna cheat or watch 🌽behind my back any chance he gets , I know that’s a touchy subject for some, but me personally it just makes me feel that I’m not attractive enough,or feel like I’m not good enough, I’ve never found evidence of cheating, and I’ve found 🌽 in his history once but I told him how I felt and he told me he understood how I felt and wouldn’t do it again,and I know the constant asking everyday and needing for reassurance with it is putting a tear in our relationship, I just want to fix it. Does anyone have any advice on how to redirect my brain whenever I start overthinking about it when I’m not around him? It just puts so much stress on me when I’m not around him cause I’m just constantly in my head about it.

I feel so bad I overthink abt everything my bf says and does. I think that if he doesn’t say x y z when I want reassurance then he must’ve stopped caring or is tired of me. I know it’s not the truth and he gives me NO reason to think this way. This is my first healthy relationship and I want to be in each others lives forever. I love him so much and I’m trying my hardest to manage these thoughts but I’m so anxious. It’s so draining I feel helpless and like I can’t go a day without checking his social medias. I want us to be the best versions of ourselves for eachother but idk where to start or how to manage this feeling.

Longer post, but please, I need some guidance. I thought that my thoughts relating to relationship OCD were taking over. But, my bf started treating me differently. I tried to have a conversation and communicate this worry. He then texted me that he had actually been feeling distant for a month and has been meaning to tell me. But “we’re fine now.” I spiraled. Later in the week, he went quiet after a disagreement. After he promised we were okay and he was okay, I found later he was texting a mutual friend (female) that I was crying again. She said that it was fucking insane and other hurtful things about me. He said he lost his trust with me because I looked through his phone and saw that message even though during the whole relationship we had a mutual understanding that we had nothing to hide from each other and he always assured me that I could look through his phone at anytime. It’s ok for boundaries to change in a relationship, but it wasn’t communicated and I was harshly reprimanded. During the texting chain with the mutual friend he also said that “she just has no idea.” When I addressed this, he then said that for the past month, he actually felt he didn’t want to be in a relationship, but still loved me. I’m ruined. I had the same thoughts in January and knew I loved him. I found out it was ROCD (through this app) and told him the day after the realization because it was eating at me. So him saying I wouldn’t understand and telling other seems unjustified. I would’ve been the most understanding. Any help would be appreciated greatly.