I have never been to a psychologist nor a doctor for my problems, so I have never been diagnosed with anything.
I am curious, however, to what exactly is wrong with me?
I thought it could possibly be Bipolar Disorder, but I don't want to jump to conclusions.

Figured no one could give me as good of an answer as those who are currently going through it, so I thought I'd describe myself a little bit and see if it was anything I should concern myself with.

I have perfectly good days. I'm happy, and I actually feel that feeling of elation just for being alive. However, later that day.. absolutely NOTHING can happen... and there's just an instant, horrifying, sinking feeling that sets in that I can't shake. It's typically accompanied by shaking hands and irritability.

It happens on a larger scale too, rather than day to day. There can be a period of time where I'm up, and I can make decisions based on what seems will make me happy... but they're such spontaneous impulses. It doesn't seem to matter to me at the time what it will do to me later. It generally has to do with relationships.
Then, later, I'll go through a time where I feel completely cynical about all of it.
For example, right now I'm in a relationship with a boy who is completely sweet, adorable, understanding.. everything. He really helps me with the issues I'm going through right now. There will be a week or so where I appreciate everything he is, and wonder how on earth I got along without him... then maybe a week later I invert and talk to myself the whole time he's around. I try and act normal, I try and make him happy... but I have this horrible feeling of doom for our relationship. I pick out every little thing that could possibly ruin it. I think out everything imaginable, silly or not.

I've moved about seven times this year on impulse, regretting most of the decisions but being completely psyched about them at the time.

Bi-Polar perhaps? Am I just weird? Could it be something else perhaps?