If i call a suicide hotline, will they call 911 if they think i'm about to hurt myself?

Yes: I can't think of any exceptions to that.

Maybe: If they truly believe that you could be a danger to yourself they will call 911. On the other hand this is not a reason to not call. If you are thinking about suicide and feeling depressed but don't have a plan or intent to harm yourself, they are not likely to call 911. If you tell them that you are not about to hurt yourself but just want to talk about it, truthfully, they probably won't.

Also, seek help: However you handle an immediate suicidal crisis, make sure you find a source of regular, competent therapeutic assistance that you trust. Suicidal ideas, especially if lead to attempts are quite serious and must feel bad. Relief may be found if you develop a relationship with a therapist to support you through times the pain is below this extreme threshold and avoid these extremely bad episodes.