Hi Jessica,
Your situation reminded me a bit of my own. My daughter is 19 and has just had treatment for anxiety and depression at University. Her doctor says she has something called dysthymia (not sure if that is exactly how it is spelt) but basically it is chronic depression/anxiety, but low level so may not cause a crisis. My daughter says reflecting back she has felt like this since she was about 13 but didn't realise that not everyone felt like that. I feel guilty that I didn't recognise this even though I have had depression problems of my own. She is naturally a worrier, competitive and has a slightly obsessive nature so that type of personality may well be more prone to this.
Do go with what someone else said and seek treatment. Our first visit to the local GP was not really helpful and he tended to dismiss my daughter by saying virtually 'get a life' and stop worrying. Her university doctor has been absolutely marvellous in recognising and helping her. Treatment with anti-depressants has transformed her. A sympathetic, listening GP can make all the difference. Do keep at it and try to get help.
Best of luck,
Tina