Ok so like I’m dating this guy, at least I think I am. I’m not sure since he never stated it but I ended up meeting his friends and I really like one of them. We’ve been dming and hanging out and he actually seems pretty chill and he kissed me today. I felt really happy that he did, it felt like fireworks but I know that it was probably a one time thing and I’m scared my bf will find out and blame me and I’ll loose both of them. I don’t know what to do about this.

Ouch, what a situation.
Okay so, first of all: in my opinion you should ask your bf something like "are we dating?", probably an uncomfortable question, I know, but things need to be clarified. Then in any case, regardless of his response, you should think abt his friend, how much do you know that guy?
You need to understand with you you're happier in my opinion.
You have to date someone you feel good/happy with.
Hope this will be helpful,,