You can not always be happy among your friends, that is true. But when you come home feeling depressed and lonley every day, that is a sign. It is a sign from your brain but not that part that physically exist but that part that mentally exist, it says “enough”. Because that is what it is. Enough.
Think about it. But not too long because then the thoughts will take over you and you will feel pain and take your friends with you in this spiral of pain. Maybe in your mind you think that the pain and sadness will be worse if you break up with your friends than what it would be if you did not. In some cases they will, they will hurt but remember that it is you who decide whether to be happy or not. It is always you who decide.
I can say that in the longterm it will feel better. For me it have been times when it only took a day before I was feeling better again. Not because I was heartless and not caring, but because I was finally free from the people that had hurt me every day and caused so much pain in that part of my life that I can not even describe it. When I broke up I felt like a prisoner who had just been released from the prison. I felt free but totally unknowing about what would happen next. What year is it? How should I dress? Act? Be? Who am I now? I was so confused. But then I called another friend and I came back on my feet again.
The sorrow of missing someone and thinking about what you two had is hard to get over but by a longer time it will feel much better. And hopefully you have found a friend that does not make you sad and depressed. Life is full of changes and you are not only living life now. Changes are good sometimes, we learn from that.