My exBF and I have were together for 2 years. I noticed him acting differently towards me about 3 weeks before?

(continued) he broke up with me. For example: he told me I could hang out with guys if I wanted. He was a very jealous person& very over protective. The next day I called him just to see if he wanted to hang out but he didn't pick up, so I texted him. He told me he was with his friend and was gonna hang out with him. So I said okay I won't bother you. We barely talked that day & I told him we needed to talk about this. The next day we made arrangements to meet up& talk and he told me that he doesn't feel the spark of the fire in our relationship anymore, he doesn't feel like BF material anymore. He said he doesn't want to be tied down. He thinks he'll be a better friend than BF. Basically he wants to enjoy his teenage years (we're both 18) and I understand that. But why wait after 2 years to tell me this? We were really serious... we gave eachother promise rings(engraved) and planned out our future. Before we began a relationship we were best friends, and @ the time I had a BF. But he begged me everyday to be his GF and told me he would treat me better etc. I don't know why but I gave him a chance and I fell in love with him. Now I can't stop thinking about him, what he's doing... its been a week and I feel an urge to call him.. but I keep telling myself not to because when I asked him if he loved me he said yes but when I asked if he was in love with me he said no.. how the hell are we supposed to be friends? What should I do?