Should i be worried/get help for feeling like this

I've been feeling really weird for the last couple of years. I don't know, i know that lots of teenagers have issues and i hope it will pass but this is really making my life harder. I get super strange sometimes, i feel so confident and i get really bubbly and talkative and i'm usually quiet and kind of bitchy.I get these rushing thoughts and i feel like they are dividing and i can't follow them and i want to write some down because they are actually good ideas but they just pass so fast...I feel happy, almost high and i feel so good about myself and i sometimes get really weird ideas that i regret later and i say some embarrassing things. And then it starts to feel like too much and i get anxious and hyper and nervous and completely irritated and i just leave class or start cleaning out my room and throwing things away it just gets too... stuffy. Last 3 months i've been having panic attacks, not extremely bad ones but they scare me, and my chest is under such a pressure all the time. I never get complete relief, i've always been like this but it never got so irritating. Sometimes i get so depressed, i've actually been mistaking it for laziness for years but now i think it might be depression, because i just feel so sad. Not like i want to cry but kind of hollow? and i just want to sleep all the time but i can't and i don't want to see anyone and i don't want to get dressed and go out and face people. I'm never suicidal though i just want to sleep until i feel better, and my grades suffer so much because of it i actually failed one year and i just didn't care at all i just felt so indifferent.This feeling sometimes lasts for months and it get almost like sickness because i feel like i'm rotting inside no matter how many showers i take. And then suddenly it's gone, i just wake up one morning and i feel okay and life is simple and good.but it comes back eventually.I get angry sometimes and i don't tell anyone i just shut down. but then i can't breathe it just gets worse so i cut my legs with a knife. I don't enjoy the pain, i don't even feel it i just feel a cold relief when i do this and i can just leave it behind so it helps. It's nothing wrong with this since it helps but i've been doing it for 7 years now and my legs look hideous, and some people actually noticed and wanted to talk about it and i just felt like a pathetic 12 year old attention seeker. I don't really talk to anyone i just try to ignore it but i feel like i need to tell someone. I'm a little embarrassed because my life is fine, i never lost anyone and my parents were good to me so i feel like i'm being a little bitch but it gets hard sometimes. do you think i should get help? a problem is that i don't have a relationship with my parents i just live with them i mean we don't trust each other stuff so i'm kind of on my own. What should i do??