I think something more serious is wrong with me?

I am twenty years of age and I was diagnosed with depression and AD-HD in the 7th grade. I am medicated for both. I also have constant bladder infections, it's normal for me to have one every month. After much testing and many doctors examining me, nothing was found. I have to drink water and this cranberry juice concentrate like crazy because if I don't the infection comes instantly. I stand at 5 feet and weigh 97lbs, which is very healthy. I eat healthy but being in college I do snack on some junk food. ...But beside all of the problems that have been addressed, I am ALWAYS tired. I can take several naps a day. My body feels week and so helpless. When I am working out at the gym or having a fun day with friends, I sometimes become very dizzy. My vision will become blurred and I even feel as if I might faint. It's normal for me have pounding headaches during all of this. I don't understand why I don't have energy and my body never feels 'good'. Please help. If you don't know what is wrong but can relate, please tell me what you do to feel better. Any help is appreciated.