Your question makes perfect sense, and I'm glad you're taking the first steps toward answering it. Please understand, however, that the experts on JA cannot (and will not) diagnose over the internet.
First of all, you are to be commended for overcoming your addiction to heroin/opiates. This is no easy task! Also, as you probably know, the use of any mild altering substance (including cannabis) can jeopardize your ongoing abstinence from heroin. You are to be commended (again) for quitting the cannabis, especially during this difficult time (the loss of your mother).
With regard to the diagnosis of Bipolar Disorder - it is essential that you see a licensed mental health professional in your area for a thorough evaluation. This evaluation will inform his/her diagnosis... which will then inform his/her treatment/therapy. Because of your complex history (recent significant loss, history of anxiety/depression, history of substance ab/use) it will be important to have a face-to-face evaluation/assessment to determine what/if you may have and how/if to proceed with treatment.
Finally, as you are searching for licensed mental health professionals to begin this process, I might encourage you to consider speaking with a Psychiatrist (MD) or Psychologist (PhD) who has extensive history in mental health assessment/diagnostics. Some folks are great therapists - but may be lousy diagnosticians. Some are great diagnosticians, but lousy therapists (like House on TV)! Right now, you need a great diagnostician.
I hope this helps. Best of luck to you.
* FEEDBACK ENCOURAGED. Please contact me prior to leaving negative feedback so that we can resolve the matter. I am eager to work with all JA clients to provide them with useful/helpful answers. Thanks again.