Can people really love someone? Can marriages really last?
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The answer to both questions is "yes".
You've been through a lot in your life. Good for you for going for therapy. If it's not working, then perhaps your therapist isn't a good fit for you---or isn't a competent therapist.
I'm surprised that once you turn 18, you will be out and fully on your own. Many states (perhaps all?) now offer support in some form or other for foster kids until they turn 21. You should ask a social worker about that.
Don't give up on therapy. If you are in a position to request another therapist, then do so. I'm sure you know that you have a long ways to go---and a lot of hard work ahead of you. In the end, it will be worth it.