I have been taking ambien on and off for two years on the advise ...

I have been taking ambien on and off for two years on the advise of my doctor (neuroligist) Ever since I had lower back surgery I have developed this irritable and shaky leg syndrome, which causes me not to sleep. I have been taking all kinds of pain medicine, which i seem to have alergic reactions to most (Hives, upset stomach etc.) The only thing that has helped me sleep is Ambien. However, I have noticed that after I eat, my stomach really hurts and i get heavy palputations (In the stomach area). About 6 weeks ago I was rushed to emergency beacause of stomach pain, bowel movement was black ( thought I had a bleeding ulcer) But they found nothing. Could this be the side affects of Ambien?