What is wrong with my body?!

I'm 18 and have a 2 month old daughter who only usually wakes up once a night. I work 25 hours a week. Anyway, no matter what time I go to bed I am always way tired the next day and I feel dizzy sometimes and random parts of my body feel bruised. My neck is really sore and a little stiff and I cannot concentrate on anything. Also, I am always way hungry. I don't know what is wrong with me or what to do. It's impairing my ability to get things done.