I agree with Soul Quake. If you genuinely do have an illness then it's highly unlikely that anything will make it better but medical intervention. If you had diabetes, would you try to wish it away with will power? I know it's scary but your best bet is to consult your doctor, at least to rule out any physical causes like a thyroid condition, and to find out whether you have a mood disorder like depression. Your visit to the doctor will be completely confidential and your doctor will be a professional -- he/she won't judge you, and will be able to give you the first viable steps for a treatment plan. The best way to get through this is to reach out for help. I put off getting help for a long time because I was scared, and like any medical condition, without treatment it just got worse. I was SO SCARED to get help, but it was honestly the best thing I ever did for myself. No matter what happens, there's no shame in mental illness, it's a medical problem like anything else, and it just needs to be treated as one. The scariest part is asking for help, but it's really worth it. I've realized that I deserved to be healthy, and so do you.

The other thing I wondered was whether you've ever had therapy or thought about talking to a therapist? Talking about how you feel, rather than keeping things bottled up inside, might actually help alleviate some of your mood swings and help you get to the bottom of what's causing you to feel this way. Also scary, but also wildly helpful in many cases. Good luck.