AITAH for being crazily obsessed at my behaviour

TL;DR: I smoked inappropriately with another girl and accidentally laid my head on her laps and got up as soon as i realised it wasnt my bag. apologised and removed every contact with that girl. I have and had no feeling of romance on her and told previously I am in a relationship. this happened a year ago and i held my guilt since then. I want to make it right but need advice.

Hello, firstly I wish everyone to know that Im not trying to frame my action as mistake and i am realising it was a wrong action. I will be honest throughout the post so please read it carefully. Also i’m very sorry for poor english.

Me and my girlfriend been dating for 3~4 years. I did a terrible thing 1 year ago and has been feeling guilty and painful since then and still haven’t decided how to deal with the issue.

I started to drink with my friends all male and there was this one girl that I wasn’t and still not interested to. We drank until late and only me, one of my friend and her was left on the drinking table. I haven’t drank for so long therefore I lost my control and drank too much. I don’t blame the alcohol for this incident happening and I know i should have controlled myself.

Anyway, three of us went out to smoke cigarettes all together all singing and laughing, putting hand shoulder to shoulder, me being in the middle.

we talked about relationships, how much i love my girlfriend, and how much i look forwards to the future with her. they talked about their life and more.

Then we sat outside at a bench and started to smoke cigarettes. Here is the part that went badly. I blowed the smoke into her mouth and made her look at my direction by turning her chin with my hand. she inhaled the smoke that i have exhaled and we did this vice versa. my friend told me off saying our face were too close to each other and that it was inappropriate in his view. he said that our lips didn’t touch and i also know for sure we didn’t kiss and i had 0 motive to do so.

at that moment i didn’t realise this was something intimate and when i woke up from the alcohol i had intense guilt and regret about it. At that moment of time i just thought it as a fun thing to do since the way smoke moved was funny for some reason. however waking up and remembering how inappropriate it was kills me until now.

Furthermore, after that I rested my head on a random spot not knowing it was on her laps, and realised it when she touched my hair and got up straight away as soon as i felt the touch, since I had and have no romantic interest towards her. it wasn’t long, but i still feel guilty for my action.

the whole night me, that girl and the guy were talking about how we should be brothers and sisters but thinking about it now I really really feel guilty.

the next day when i woke up, I thought back to my actions and felt intense guilt. i told the girl that i will cut off her contacts since i feel like it’s going to disrespect my girlfriend and she said it’s perfectly fine. Tbh I avoided people since then and became completely anti social since then because of self hatred, and self punishment.

Because of the guilt I tried to tell my girlfriend about it. however my girlfriend also caused similar issue at the beginning of our relationship. she told me honestly, and it did help me grow so much as a individual. however I did feel intense pain and it did cause me to be really unstable at that time also wishing that she would have hidden it from me.

I am still thinking about it for a year if i should tell her or not. I feel like telling her is selfish, and i’m doing it just because I want to let go of my guilt. however keeping it in haunts me deadly and I lost so much weight since then because of the guilt. please give me advice.