I feel like I'm having a breakdown or getting depressed?

My name is Mike and Im 17. I'm asking this question while tears are coming out of my eyes and I am unable to get to sleep because I feel like so much crap. Honestly, right now I feel like a good for nothing person who just can't seem to get anything right. All my life I have been EXTREMELY hard on myself from anything to sports, especially baseball to random things. If I feel I do something wrong I put myself down as much as possible until I feel I am unable to do anything. I can't help it though, I am just like hat. It feels like I'm having a battle with myself and my mind always wins. The past few days when I've been playing baseball for my high school team, I have not been playing well at all which is heartbreaking for me because I feel it is all I have and am so passionate about the game. If I don't get a hit in a game I have a war with myself that night because I can't shake the thoughts of me doing bad. I think about it the next day as well which leaves me with no confidence for anything. It basically sucks everything out of me. I slam my foot down in the dugout, I indirectly direct my frustration at my teammates and friends, which isn't good for anyone. And on top of that, I've been texting the girl who I feel I may be falling in love with. I've been talking to her for about 1 month now and haven't seen her since then. I go to school with her and she is always on my mind. I just get worried that she is going to slip away from me and never want to talk to me again. What it comes down to is that I don't feel good about myself at all and need something, anything to get myself to calm down and get rid of my own demons. Thanks :)