The guy I am talking to is hanging out with my friend. What should i do?

Okay so me and this guy are hanging out and I am just trying to see where it goes with him. One time me, my guy, and my girl friend all hungout together and had a good time together and they have been talking about me and one time he asked if she would like to come over to his house if a party didn't fall through because i was out of town. He texted me the other day and told me that MY BEST FRIEND and him went out to lunch at tomato head the other day and they made plans for all three of us to hangout. I was weirded out that they hungout without me especially since they have only hungout once together? My best friend never told me about it, and I told my boy that it bothered me and all he said was sorry. He texted me today saying he wants to talk and that he sometimes forgets about other people's needs when he wants something. He believes that i am unsure about what kind of relationship i want. I want him to know that him hanging out one on one was out of line, because he has no need nosing into my friends when i don't hangout with his. What exactly should i respond back to his text?? I need major help please