There are reasons why some people cannot hang onto a relationship, sometimes it's their fault, sometimes it's the other person's fault, you need to examine what you're doing, if what you have been doing has not been working then try the opposite, that may work well for you, if your depression feels so deep then maybe you need to seek some form of counseling, I hope you feel better, I know you will...smile...)
After dealing with it myself, and still am working through some things, it's really good if you can find someone to talk to face to face or at least by phone. Talk through everything. It may help to see a counselor as well. Know this. You are worth a lot to many people. I don't know what you believe, but I've got to at least share this with you. Jesus loves you tremendously! If you ever feel like you don't have anyone, I promise He is there wanting you to bring all your hurt and pain to Him. 1 Peter 5:7 in the Bible says, "Cast all your cares on the Lord because He cares for you." You are loved!
stay busy, don't let nothing get u down and exercise is good, another option would be searching for help at hotlines. oh and stay close to your love ones, cause they're the only one who will be there when times are rough.
It's always hard to lose a loved one. Trust me when I tell you this: He was not the one. Anything that is meant to be will be, at the right time. Have confidence in yourself. You are a strong, independent, beautiful person; in and out. You don't need him. If you broke up with him, remember why. If he broke up with you, then it's his loss. When you find your depression especially excruciating, look around you and find three things to be happy for, three things to be grateful for, three things that make you feel safe, and three things that you love. Then explain why each one makes you happy, why each one makes you grateful, why each one makes you feel safe, why you love each one. It works on me every time. Good luck, I know you can do it. You are capable of anything. You will find the right guy some day, just be patient.