I keep on waking up in the night - why?

l am getting so fed up of it now. l have to work and go to college so it is tiring me out! l go to bed around 11PM and wake up at 2AM then again at 4AM and by then, l can't go back to sleep so l have to stay awake until 7AM to get ready and then l am so tired but l have no choice as l have to go to work. l have tried everything from destressing and drinking hot milk & honey. l do have anxiety issues but l am sorting those out and l go to the gym every day for one hour after work to make me tired later but that doesn't work either. What else could it be? l'm in a silent environment so noises is not the culprit. l'm 18! Thanks.