Missing my ex...

My ex-boyfriend and I just ended a 2 year relationship & it hurts so bad. We started dating our junior year of high school, and we had a great relationship. We did soo much together & made so many memories. We are both 18 and getting ready to start college soon (going to same school). But, things started to feel different. Not in like a bad way, but we just started changing as individuals. Also, we both have busy work lives. He texted me one day and said he felt that we were growing apart and the past few times together felt weird, which I guess was kind of true. It’s so just hard for me because I feel there was really no closure. I asked him could we talk about it later because we were both going to work at the time & he said yeah. He never called me or texted me back. I feel that I still have an attachment to him & it’s hard to let go of of. I miss our relationship so much.. I can’t stop thinking about him and crying. Does anyone have advice on how to deal with this?