Dear Aussie English Girl~
Welcome here to the Forum, it sounds very much as if you need someone other than your mother to assess how you really are. Trying to do it yourself is not always successful as you are too close, and from the sound if it your mother jumps to conclusions and regards some people as 'psycho', a demeaning and meaningless word no professional person would use.
Having an intellectual delay would be something that would be extremely hard to deal with, constantly trying to understand everything- if there is time and matters have not moved on to something else. As a result I think I'd be both frustrated and angry -at the very least.
May I suggest you go see a doctor and explain what has been happening, and about the worry over bipolar and PTSD? Get a professional opinion by someone qualified to do so and you will know where you stand.
Do you think that might be possible to do?