Taking a medicine for the side effects is not really a good idea, especially without working with a doctor. There are other possible side effects and you have no way of knowing if the weight loss or other help will happen again and/or the repeated losing/gaining back can change your body in ways not healthful for you. You say you cannot lose the weight but it does not sound like you have ever tried in a healthy manner to do so (if you automatically eat poorly when your boyfriend is around).

I do not know what your circumstances were when you originally saw a doctor and received the medicine but if an adult paid or you were in a special program; I'd contact the person helping you and see if they will continue helping you (by paying for doctor appointments, etc.).

If you primarily just want to lose weight, I would work on learning healthy ways to do that, how to eat and exercise effectively and give that a try rather than rely on pills that may/may not work or mess up your life worse. Just going to a better eating plan so you are only eating 1500 calories a day and getting a bit of activity will lose the weight again, a pill that suppresses appetite cannot be used forever or will make you very ill and in worse shape than you were in the first place and dependent on it instead of your own hard work.