Bless your heart. You're going thru the toughest time emotionally than you'll ever go through in your life. The teen years (yes, even eighteen) are the WORST years you'll ever spend.
My teens were horrible -- I would never go back there for all the money on earth. Our bodies are changing so rapidly, and the chemicals in our brain are also doing the same thing! These chemicals are TRYING to level themselves out to an "even keel" to where we can act "normally" (whatever that is) and FEEL emotionally safe and secure. Trouble is, during the teen years, we don't feel like that. Nothing "works right." Everything is out of whack! The body seems to be fighting itself, trying to grow up! It's AWFUL.
Then, lo and behold, we get into our twenties and things DO level out and all of a sudden we find we're an adult -- and all that chaos is gone!
The trouble is, some young people in their teens DO need therapy and you might be one of them. And the OTHER trouble is --- parents.

A lot of parents think that if the teen comes to them and asks them if they can go to therapy, the parents think it's just for "attention." Well, it's NOT. I wish parents would WAKE UP and LISTEN to their kids!!! I had my 15 yr old (at the time) granddaughter living with me for a time, and I noticed she was depressed, and HAD been -- so I took her fanny to a therapist! Her parents had split up, and obviously she was effected! She's 17 now, and STILL in therapy so she DOES have issues.
Talk to your parents -- calmly and nicely. Ask them to please make an appointment for you with a therapist - or have your doctor refer you to one. Explain to them that you're extremely depressed, irritable, etc. Make SURE they know this is NOT any plea for attention! I hope they'll make the call for you.
God bless and let us know what happens. Hugs, Lee