There is something that you can do anywhere that works great to get you in a better mood and have a little bit better of self esteem and no one has to know about it. Write things that you don't like about yourself. For every bad thing you write, write two things that you like about yourself or others like about you. Repeat this as much as you like until you get the picture.
I'll do an example,
I have so many disorders it isn't funny - I am musically inclined, I am a nice person (from others)
My school marks are dropping lately - I am mechanically inclined, I am good at helping others (from others)
You don't have to use some from other people if you don't want to, but if you are stuck then do so. If you are too afraid to ask a friend, talk to me, or anyone else here on this site, I'm sure they will be happy to help.