Okay, I know that suicide is NEVER the answer

Lately, I have been really down. Like depressed. I didn't leave the house last weekend. I have been forcing myself to go to work for the last two days. I teach, and today I had to leave the classroom because I thought that I was about to snap on my students. Don't get me wrong, my students are some of the worse behaved kids in the school, but I've molded them, and when I'm off, they know it! I have no motivation within my self, and has literally thought of suicide. I just don't know why I've been feeling like this.