Mental/ emotional issues. Do I have a serious problem?

So.. just to give you some background about myself: I'm 23 years old, single. I was in a relationship but we broke up few months ago. I can describe my life as always being somewhat unstable.. I always felt like I was under some pressure. The weird thing is that it doesn't show on my face. A teacher once asked me why I'm so careless about everything as if it doesn't matter, in reality I wasn't. I was silent most of the time in class.. was afraid of speaking and didn't have many friends. I'm afraid of opening up. I want to mention that I was a good student most of the time.. so I'm not dumb. I went through a tough phase in school were my grades were getting worse.

Now I feel ok. But Im scared that it will ruin my life. Recently I have this thing where when I'm completely alone.. I just start crying out of nowhere. But when I'm around others I act normal. Also lately I'm thinking about death.. not wanting to die or smth but being afraid of what comes after and about the people I care about. I don't have many friends or any close friend.
Someone has advice?
Mental/ emotional issues. Do I have a serious problem?
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