Greetings everyone.

Last Saturday me (21f) and my boyfriend (24) went out partying with some close friends. We all had a blast, so we moved down to our local pub during the evening and continued drinking.
So, I am bisexual and my boyfriend knows this and he’s very supportive. We have been talking about potentially having a threesome with another girl, and I have been very open (so has he) about the idea. During the evening I made out with one of my girl friends while my boyfriend sat next to me; we were ALL consensual about this, my boyfriend cheered me on and encouraged me to do it, because he knows I’ve never kissed or been with a girl before. It felt good when it happened, and I made sure both me and my friend was comfortable with it happening.
Skip to the day after, I was practically bawling my eyes out, feeling like a piece of shit for what I had done. My boyfriend kept reassuring me that I had done nothing wrong, that he was also in on it and that I had no reason to feel ashamed. I still can’t shake that feeling away, and I am basically feeling so awful I want to commit suicide or get back into hard drugs to cope with these feelings.
How can I just… accept that it happened and not go to such extreme lengths about it?