Please help

A person I was involved with came by my room and came in without my say so.... I told him I was busy and was walking him out and he kissed me I pushed him away and told him to stop.... I've been dating a guy for two months and I love my boyfriend so much..... I kicked the guy out and couldn't sleep that night.... I want to tell my boyfriend. Girls have cheated on him before and I don't want to be in that group.... I love my boyfriend with all my heart and I can't bear the thought of betraying him..... Please help me..... I've gone through what I'm going to tell him so many times my head is killing me..... I don't want him to think I hate him and don't love him, what should I do girls? Also I don't want him to just rage and get into a fight with the other guy.... It will be bad and I just can't have that, it will make my boyfriend seem like the bad guy.... Girls.... Help me?