Depressed and Friendless

Okay. I have a bit of a long post so stay with me here. I suffer from chronic daily migraines and major depression. This being said I was suicidal on Saturday, not the first time not the last, and I reached out to two very close friends. The one responded immediately and called me to make sure I was okay. The other who I consider my best friend in college didn't respond until a day later, and this is not the first time I've reached out to her and had her do nothing. The one time we were taking and I told her and she just stopped talking to me. She has bipolar manic depressive disorder and I have always always been there for her, I ran redlights and have called campus security to help her. I feel like the relationship is toxic but I also don't know. Most of the friendships, if not all are always me giving and not getting anything in return. I don't know what to do and I'm so tired of people using me. Help.