My head is all over the place..?

All this started when i was 11, and i started high school. Everything was simple before that. Then it all got complicated. i got really depressed, but i wasn't always depressed, and that used to bother me too. when i think about how i used to feel when i was depressed, all i see is black and white, grey hazed images of random clrooms, and those few nights i used to cry under my pillow. i remember feeling bad about feeling depressed, i thought about telling someone but i was scared of what people would think of me. it was all in my head, but it was so real. the thing is, when i went through these depressed months, i wasn't always down. i could be happy for a bit.. there were people capable of cheering me up. then i fell in love. i'm really shy, i have mive self esteem issues. i know i'll never be good enough, but just being near him makes me haappy, even if we don't really speak. after i had the depression stage, i had a stage where i went from being really depressed to happy and fidgetty, and HYPER. then i got into i stage where i got very pissed off at everything. i never show when i'm angry, i keep it inside and never let it out. i think the keeping my anger in and low self esteem is what's caused all this, but i don't know how to stop it. my head is still all over the place, and i don't know what to do, or how to be happy for once. also how did i get over the depression? will it come back? how do i improve my self esteem? thanks:)