Wow. This isn't an exaggeration, you sound exactly like me. I have studied psychology at A-Level, struggle to be open with anyone (regardless of relationship) but always tell the people closest to me being open is extremely important.

Something that happens a lot with people studying things like medical science and psychology, they develop something called "medical student syndrome", basically where, because they have to learn a lot of about the signs and symptoms of certain conditions, they begin to notice signs in themselves they wouldn't have noticed before when there they really have nothing wrong with them at all.

Not to say that is you, but I do the same thing and have done most of my life. I think I have things when I don't (or think I have something else instead of what I really have), so the best thing is to get a professional diagnosis. Being hypocritical again (LOL), I struggle a lot with mental health and refuse to go and see a professional (if I have anything I'm high functioning enough to struggle though life).
We should take out own advice, haha.

Peace.