How long should i leave it b4 going to the doctors about depression ?

I am 17 n suffared with depression for a year in year 10 n then it went away now I'm feelin depressed again it has only been 2 to 5 days its been back but I hate feelin like tis n I'm scared it will come back for a year or like forever I no it feels worse tis time but I don't know if its a bad wk my sysmtons r I'm feelin down consentally, lonely, want to be on my own, thinkin of past a lot, I don't like my self i feel stupid but also ugly n fat family members I miss I miss more I'm cryin so much more over silly stuff so could u tell me wat I should do n whether I'm over exaderating n it isn't depression n how long I should leave it so I no it isn't a faze also wen I'm around certain ppl I don't fell this way I fell fine plz help n I'm consentally listenin to a depresiing song over n over again