Adderall XR and cardiovascular problems

just started taking Adderall, though i am not prescribed. I went to my doctor and asked for it but she said no. I explained that I am often overwhelmed at work, I am a case manager and keeping on task with all of the work is hard. My doctor said when she was in med school, med students used to take it for that purpose.So anyway i bought 5 pills from a coworker. I seem to have super human energy, get all types of work done and stay focused all day. On the down side, in 5 days I have lost 3lbs., I want to lose weight, but not that fast. I have what I consider to be Adderall hangovers the next day, where I am extremely tired. I also have noticed severe headaches, every day that I have taken it, I crash by the end of the day at work and cant wait to get home, because I am so tired. My neck aches, and I had to change to a firmer chair at work, because all of a sudden my back is killing me, I also get insomnia and have to counteract the Aderall with Tylenol pm just to get to sleep. These side effects freak me out, and I don't know if I want to again ask my doctor for a script, but I get so much done at work, and I am heading back for grad school, I just don't know what to do? oh yeah, the pills that I bought were Adderall XR 30 mg.