Should I [21f] tell my boyfriend [22m]

My boyfriend and I have been together for almost 4 years now. I’ve never loved someone as much as I’ve loved this man. He is my sun, my stars, my moon, and everything in between. I want nothing more than to make him happy and give him the life he deserves. Unfortunately, I haven’t always been this way.

We got together in high school when I was 17. He had the biggest crush on me and did so many sweet and thoughtful things. I did really like him to start off but I was so self centered in high school. All I thought about was myself and who I was gonna be and what I wanted out of life. Looking back on things, I feel so poorly for having taken him for granted. About 7 months into the relationship, I decided to break it off with him. I remember feeling like I was leading him on because I just didn’t know if I had feelings for him and I was also struggling with my sexuality at the time. I wasn’t able to see him in person so I sent him a message saying that he was a great friend and that I really cared for him but felt like our connection was gone and that maybe it would work in the future but it just wasn’t working now.

Here’s where the problem comes in. The same day I decided to break things off with him I was messaging a friend from high school. I didn’t have a crush on this girl nor did I find her attractive. I did know that she had a crush on me and I think I just really wanted that attention from a girl because I was confused about myself. After spending the last month obsessively thinking about this event, I eventually caved and requested a data retrieval from SC because I no longer had the messages. After going all the way back 3 years, I found our messages and I became flirty with this girl directly after breaking it off with my boyfriend. I mean like 3 minutes at most. She was already being somewhat flirty towards me but I didn’t flirt back until having messaged him. I don’t think I intended for it to go this way but after my newfound “freedom” I decided to be a little flirty.

By flirty, I don’t mean sexting or anything inappropriate. Just stupid teenage flirty behavior. I called her pretty and we talked about what we found attractive about women. The flirtiest it got was her asking me if I had any turn ons because we were playing 21 questions to which my 17 year old brain replied “idk, neck kisses?”. That was as bad as it got. She did eventually express an interest in wanting to hang out which I wasn’t comfortable with so I messaged her the next morning and said I wasn’t interested and wasn’t gay. I apologized for leading her on and said that it was very out of character for me. That was the end of that. It was like 10 hour convo that went no where.

My boyfriend and I ended up getting back together a few months later and I fell head over heels for him. Idk what I was thinking then. I just remember being so self centered and having no idea who I was. I want to tell him about it because I feel so bad for flirting with a girl minutes after breaking up with him. I know he was heartbroken and even if I didn’t have feeling at the time, it was such a shitty thing to do.

My therapist said that this sounds like a normal teenage thing to do and that I need to learn to control my obsessive thoughts but I feel like this is different. I feel like if I don’t tell him then I’m keeping it a secret. We’ve been dating now for 4 years and I feel like I owe him the honesty. Everyone else has told me to move past it, and that telling him would just hurt his feelings and maybe even make him question me for still thinking about it 4 years later. I haven’t thought of it until this last month but now that I have remembered it, I can’t stop thinking about it.

Do I tell him for honesty sake or do I keep it to myself? Should I feel as shitty as I do or was this just a mistake in my past? Everyone is telling me the opposite of what my brain is feeling.