What can I do to stop feeling this way?

Ever since I can remember I have been a worrier. Once I had my son 3 and a half years ago, I became not only a worrier for myself but for my son as well. I had a daughter 9 months ago and had a terrible birthing experience. Needing a blood transfusion afterwards. Since then my worrying has been a lot worse. I always think there is something wrong with me or my children. I understand kids get colds, but I automatically think something else is wrong. I am constantly feeling for lumps and concerned that something will happen to my children or myself. I am afraid of my kids growing up without me or something happening to my kids. I went to my dr. and he said it was a type of Obsessive Compulsive Disorder and put me on medicine. I could not function on it(i forget what it was) I was extremely tired and had bad dreams at night. I go back to the dr. to discuss this with him, but really just want to stop feeling like this. I really feel like this gives me much anxiety and affects my daily life in a negative way. Please help.