Ritalin Addiction

I am in desperate need for answers. I have always had severe anxiety and trouble controlling it. About 5 years ago my doctor put me on Lexapro and I have been on that since then. Prior to that I was diagnosed with ADD and since 10th grade in high school I have been taking some form of stimulant. I use to take a very low dose, 15 mgs a day, and only some days. I rarely took it in the summer or on weekends, if ever. I continued this pattern through high school and into college. When I started college I would not take it that often, and it was still about 20mgs, as prescribed. I would never take it on the weekends. Now I am in my junior year of college and for the first time am very worried about my Ritalin use. I have gotten into a habit of taking Ritalin everyday. I will not go a day without taking it, even if I do not have homework to do, I will do other assignments early. For the first time I started taking it just to clean my room, or if I didn’t have homework to do. Now I make sure that I take it everyday, even on weekends, and even on vacations. I often take it and don’t end up doing the work I intended. I usually take 60 mgs at once, and then 20 more as an hour or so goes by. I know this is an unhealthy dose. But when I tried to go down, I just felt very depressed. Also, my anxiety increases a LOT when I take Ritalin, but I still feel the need to take it. Im just confused as to what happened, why I now feel like I must take it everyday, does this mean I am addicted? As low a dose does not work anymore, so I just increase it by myself. More recently I have become VERY anxious and scared about being addicted, and reading about depression with withdrawl (withdrawal) scares me even more. I just don’t know what happened, if I can get back to a lower dose, and not feeling like I need to take it every day, and if I am in fact addicted. I feel like going out with friends less, but I still feel like I need to take it. The thing is I wouldn’t be able to concentrate with out it. I need to know if I can break this habit but still use it, I’m very confused and don’t know what this means or what I should do. Im scared to turn to my docotor because I don’t want them to take my perscriptin away because I need it to do homework, I cant without it. But I don’t want to suffer from severe depression when I do go off the medication. I need to know what constitutes as addiction and if I can get back to my old habits