You are certinly not a slut. This is something you need to discuss w/ your T. Letting others convence you to do things you are not comfortable w/ is something you need to develop skills to be able to handle them and to be able to walk away. I myself am terrible at this. I get myself in more trouble this way. Not sexually, but doing things I am not sure is right or not and knowing until later it was not such a good idea. ex. saving a kitten a knowing I am going to get in trouble when I get home w/ it. Better to learn how to handle life's mysteries now instead of when you are older.

I agree though you should let this other person know you should not have participated in the things you did. Hopefully he will feel the same or at least not pressure you to do it again in the future. I hope your relationship w/ this individual works out the way you want it to.