Chemical Imbalance
First, what type of "chemical imbalance?" Second, how do you know you have one? Third, don't ever...ever, ever...do a home fix for brain chemistry. Messing with your junk is enough. Your dome is far too complex and risky. Go see a professional and get a qualified diagnosis.
If you are dealing with an imbalance in brain chemistry, you can be dealing with depression, mood disorders like bipolar/manic depression, schizophrenia, and a host of others. Each has its own treatment, and selecting the wrong treatment can lead to catastrophic results. For example, giving a manic depressive certain anti-depressants can send them into a profoundly risky delusional mania. Similarly, treating a clinically depressed person with simple mood stabilizers can be ineffective and end in a suicide.
See a pro...fifteen years or more of education and clinical studies can come in handy. There are many free services available. If you get a diagnosis, it is likely that there are inexpensive foreign drug sources available if you are uninsured.