What should I do

We other high school sweet hearts. We grow up together. Our family have know one other before we were born. My ex - boyfriend and I were dating for 2 years and 2 months. Then we become best of friends. Then we try dating for the two time. I call it off the two time because I was trying to go to college full time and work full time it was too much to me. Now we are best friends. He want to be friends that have sex with no relationship. And I can not handle seeing him with ohter girls. He can not handle seeing me with other guys. But he doesn’t want to dating me again. He said to me maybe in the future we will go out again. He wants to see other girls. He is going to be 21 in Aug. He wants me to be there at his party, but he wants his girlfiend to be there also. What should I do.