Would it help to keep a mood chart, draw out a scale 0 to 5 or 0 to 10 (use minus if it helps you) where 0 is ok and the top number is the worst you can imagine, with the date on the other axis. Put a cross next to your score for that date at the end of each day and note if anything big happens like an exam, a rare visit from family/friend or an argument with someone, whatever is significant for you. (I don't necessarily note an event for every day, just something which could change how I feel)

It will take a couple of months to build up the data, but it can help you to see patterns and then you can show the doctor. They generally like charts and concrete things, it is more substantial than a vague tale of woe, however desperate you are.

I'm lucky enough to have a good family doctor, and we tried HRT to see if menopause changes were affecting my mood. I had a chart from one month before the treatment and the 2.5 months of treatment and it seemed to help us make the decision that, sadly it didn't help.

There may be examples of charts online, don't make it too detailed if you might become obsessive about it, and doing too much detail can be hard to keep up.

Just a thought, but I know they like as much objective information as possible to help them make a difference. It also shows you're trying to help yourself.

Best of luck, and if there is an alternative doctor in your practice you can go to, it may be worth trying them (armed with the information)