I am depressed and I don't know what to do anymore
Sounds to me like you are depressed and mourning. Essentially, you are suffering a significant loss and you seem to be grieving the loss. That is totally ok to do right now considering the fact that you were probably very close with your boyfriend. At some point, you will have to move from mourning the loss towards honoring it and allowing that wound to heal so that you can move forward.
It sounds cliche, but you have to be good on your own before you can be good with anyone else. Many people get into relationships just because they are "afraid" of being alone or when they are not mentally or emotionally stable. Typically, those relationships wind up being with significant others who are toxic and further hurt/traumatize the other person.
Learn to love you. Place your focus on your needs not your wants. There is a distinct difference. Wants are typically superficial and/or materialistic. "I want a sports car, but I can live without it." You can't survive without having your needs met. You can use food and water for examples. If you don't have those, you could not survive. So put it into practice. Do you want or need a significant other? Do you want or need to go on a vacation? Do you want or need to go out and party tonight?
When in a relationship, you want to pay attention to resentment as well since that is the catalyst for relationship decompensation. It usually happens when one or both people in a relationship are not getting there physical or emotional needs met. They try to voice their need for change to occur, but the other person doesn't change. Then the resentment grows until the relationship falls apart (break up, cheating, divorce, etc.). Also, you are an individual and have your own path. Just because other people have careers and families doesn't mean you are "behind the ball". It just means you haven't gotten there yet. You will in your own time. If you want to start a career, then that is what you do. If you want to go to see a movie, then go. You don't need anyone else, but you.