Please wait until you have your intake before you label yourself with a diagnosis. There are several things that have some of the symptoms you describe. For example, borderline personality disorder included rapid changes in mood and self-harm. Keep an open mind until you see the psychiatrist.
Perhaps once you get on some medication it will be easier to get off the pot. You have already taken a big step in the right direction by seeking help. The medications will help but they are no cure. You might do good by seeing a therapist to help you learn some coping skills.
Meds can make a real difference although it may take more than one try to get it right so if the first ones don't work - don't give up.
Going to a psychiatrist is the first step. And as hard as it may be, be brutally honest. Trust me they've heard it all, and then a little.
I know some people who use pot to manage their bipolar, but they don't seem very successful at it. And nowadays pot is seldom just pot. It is often mixed with all kinds of other 'enhancers' to get you addicted. Just be careful, and in my opinion it is a really bad idea to self medicate.
Good luck.
The best thing to do is just to let the psychiatrist know what is happening and then they would be able to provide an appropriate diagnosis and treatment with the information. Also keep a mood tracker and print out the results for the psychiatrist. Sudden shifts in mood and outbursts of anger can occur in rapid cycling and mixed states but only a psychiatrist would understand whether that would apply or not. It would be best to discontinue smoking as that can worsen and trigger mood episodes over time but if that is difficult you can discuss that with the psychiatrist as well. In the meantime this is some helpful information you could read up on and discuss with the psychiatrist when you see them:
http://www.medhelp.org/tags/health_page/167/Depression/Useful-Bipolar--Depression-Webisites?hp_id=523