I need advice. please help me

I am 18 years old and my name is sarah, it started with biting my nails when I was 6 , and got worse as I got older, I've tried everything to stop but I just can't! Not only that, but now it's almost my whole body. I bite my nails, i chew at the skin around my nails until they bleed, i chew inside my cheek, i chew my lips, i chew my tongue, i pick at my head until there are spots that bleed, i pick at my pimples, i pick at the skin at the bottom of my feet until it bleeds, It seems like when i try to stop one area, another area gets worse. It's so embarrassing and hard to hide, especially the scabs and bloody spots on my scalp. I really don't know how to stop, i'm constantly doing it, if i don't do it, then i feel almost panicked and fidgety. I want to stop so bad it's driving me crazy and making me depressed and disgusted with my body. But I barely have enough money for food, i cant afford some of the things this site is suggesting, like doctor or counselor.