How to breakup with bf

Hi,

I figured out I might want to breakup with my boyfriend. We had been together for two and a half year now. We know each other for 7 years or so.

Before having a relationship, we were having a thing but I did not like the fact that we were hiding it in front of other people. So I moved on and left him for 3 months or so.

Then we got together after he wanted me to try it again. It had been really nice, he was what made me happy. But I feel like I don't feel the same way anymore.

He was away for a year or so in total while we were in a relationship, working abroad. I knew he had to and I was able to wait for him, I told him I would.

Now he is back. But I feel like I got used to being without him. I love when I am with him, and it Is breaking my heart to leave the city when coming back to the city where I go to college. Then I am here, and I feel like a different person. I don't feel like I love him when I am away. Suddenly I don't miss him.

He has no one but me. His parents are dead, his family is horrible. I feel terrible in this situation, he told me that the last time I left him, he was not able to live properly. I am worried about his reaction. But I feel like I should move on and don't know how to address the situation to him. This distance is driving me crazy but my university is exhausting and I don't really have time to have a relationship. I know he would be able to wait for me... He would do anything to stay with me. But I just don't want to live like that, I will study for the next 4 years. I feel like I don't deserve him at this point. My mind is just straight focused on school. When I come back, I rush to his place but then I am really disappointed I got distracted and did not study enough...

How should I start this conversation? I think he has no idea, I don't want to hurt him. But I know I am being selfish, staying in this relationship.

Also the question is, do I start the conversation in person after I will be able to get back to him (which is in February) or is it okay to deal with this via messages, since we don't get to see each other that often? What would you do? I am really bad in interaction and addressing these types of things...