Tiredness, Drowsiness, Sleeping Difficulty, Continuous Headaches, Low Concentration Levels. How Can I Overcome This?

Hi, Im an 18 year old girl, I ve been feeling really tired and exhausted almost all the time and drouzy even though i have trouble falling asleep fast (sometimes it takes me two hours to finally fall asleep), i have headaches most of the time as well. I m in med school and i always find it hard to concentrate during lectures, labs, and even when im studying at home. I m falling behind with my studies, and i feel depressed and cornered. this has been going on for almost a year now, I ve become more isolated and very irritable. My diet isnt unhealthy at all, I eat fruits and vegetables and protein everyday, low fat and only have one cup of coffee in the morning, and its still not helping me concentrate or feel more alert. I ve been taking iron supplements and vitamin A supplements for 3 weeks now, see no difference still. what can i do to be more alert when i need to, sleep well, and be less tired? thank you