Keep a mood diary. Google it, and you will find a lot of suggestions to how to do it. It will make it easier for you to discover if there is a pattern to your moodswings, and ups and downs. Also it will make it easier for a psychiatrist to help you if he knows a lot about your symptoms. Remember that psychiatrists only know what we tell them, and that is basically what he/she has to go on when making a diagnosis when it comes to MI.
Make sure you get enough water and eat properly. If it is a problem getting enough nutrition, take some supplements. Ask your doctor to take bloodtests to see if you have any deficiancies in vitamins. If you have that, it will make everything worse. Also try to get some fresh air every day. Only ten minutes if that is all you can manage. These things help me when I am going through severe ups or downs. I am bi-polar. I think you are doing a great thing for yourself by getting professional help!