Do I have a mental illness?

Do I have a mental illness? I think that I possibly may have some kind of mental illness, but I can't really understand which or anything so I'm asking on this app if anyone can help me.

So, in my life I have changed a ton of times. My mood always changes, I change as a person as well as my goals in life change too. Sometimes I just can't figure out who I am at all. I just don't know. All of these things can sometimes frustrate me and cause mental breakdowns, feelings of emptiness or self harm. Suicidal thoughts can sometimes be there as well. I can be overly happy and then suddenly overly sad and then when I go through all of those feelings, it can cause emptiness and possibly an existential questioning. I hate myself for this and am kind of sensitive about it, but if you know if I have a mental illness through this description, please tell. Ask me further questions if you want to, I ll answer. Thanks.