hi apple&strawberry, welcome to PC

I don't have much to add beyond what others have said, but I agree, seeing your GP would be the best idea for you right now. Whether it's your birth control or depression causing your low moods, know that there is no such thing as "insignificant" problems here. The upside to having depression is that we are very attuned to others' distress, and we know that big and small things can all have a huge impact on our lives and mental health.

Does your uni have a student support service? That's where I go right now to talk about my problems with a counsellor. It's free and entirely confidential. A good number of UK universities also have a service called Nightline (or something similar) that's a confidential listening service run by students, where you can call and talk about your problems anonymously and confidentially. I would urge you to use one (or both) of these services. You are not the only person your age, in your year, or in your school with self-esteem and mood problems. It sounds to me like you suffered quite a lot of emotional trauma at school and it's no wonder you're feeling the way you do now! Talking it out with a professional might help you work through some of the feelings you're having, and get you on a path to higher self-esteem. I suffer from depression and debilitating low self-esteem, and talking to a counsellor has done wonders for me. A counsellor will never tell you to "just get over it", and no issue is too big or small for them to help with.

This is a safe space to come with the things that are bothering you. I'm glad you posted, and I hope that you post again to let us know how you're doing.