You're worrying about a lot, more than you need to be worrying about if we're being completely honest. The minute you wake up things start flooding your brain faster than you can sort them out.
Its okay that you skip class sometimes. Not everyone is perfect. So what, you overslept and now you're going to beat yourself up about it? Chill out, go back to sleep, and try again next time.
It's okay that you aren't the skinniest. Are you happy? That is all that matters in the long run. Who cares if you aren't stick thin all the time. Eat a large pizza if you want to. Go to the gym and eat right if you want to. Don't do what you think society wants you to do.
It's okay that you don't have a boyfriend. Seeing girls in perfect relationships sucks. We do know, however, that what they have may not be perfect. Remember that not every relationship is lived exactly how it is portrayed. You are probably way happier alone than they are in a relationship.
It's okay that you don't know what you want to do. Today, tomorrow, or in ten years, its totally normal to not have a plan set in stone. Life is scary. Shit gets tough a lot. One tragic event, one denied loan, or one mess up can completely screw up any plan. Don't worry, girl. Things happen for a reason. You'll end up where you need to end up.
It's okay if certain people don't like you. You can't help who you are. The only person you can be is you. Take pride in who you are, have your own morals and standards, and hold up a big middle finger to anyone who is in your way. So what if some girl doesn't like you? Carry on.
It's okay to say no. You don't have to say yes to everything. You don't have to be the president of everything, you don't have to be on every committee, and you sure as hell don't owe anyone anything. Know your limits. Don't fill your plate up too much, because then you'll have no room for desert.
It's okay to doubt yourself. Having self confidence is a very important part of someones personality, but so is their ability to doubt themselves. Most of the time when you doubt yourself you end up impressing yourself in the end. So go ahead and set low standards for yourself, because I guarantee you're going to blow yourself away when its all said and done.
It's okay to worry. Say what?! You heard me. Its okay to worry, sometimes. Its okay to worry about a test grade, an application, etc. So don't waste your time worrying about yourself. You are doing just fine.