Even if this isn't Bipolar disorder, you should still see a doctor. It sounds like these symptoms are disrupting your life. I think you should go to your regular doctor and get a physical first. Some common things can cause some of these symptoms, such as hormonal imbalances like with your thyroid or other things. Lack of sleep alone can cause mood swings, depression, forgetfulness, etc.
If they cannot find anything wrong, then you should talk to a psychiatrist about Bipolar disorder. Don't let your regular doctor diagnose you with something like that because he may not be experienced enough. You don't want to get diagnosed with something if you don't. have it.
By writing this, you know that something is wrong, so don't ignore it or put off getting this checked. The sooner this gets treated, regardless of the cause, the easier it is going to be and the quicker you will feel like yourself again. Write back if you have any other questions.