I have been feeling sick to my stomach and a little light headed like i could black out. i have blacked a few times in the past what could this be?

Light headed: The combination of feeling lightheaded and stomach upset raises the question of an ulcer, with possible bleeding (? Black stools). In women of reproductive age, pregnancy is a possibility. Significant acute stress can also do it. Because these symptoms are potentially quite serious, i would advise that you check with a physician.

See your doctor: If you mean "passed out" when you say blacked out. Losing consciousness is always abnormal, and can be a symptom of many serious medical problems, from the neurological (seizures) to cardiovascular (abnormal heart rhythms), as well as from clots going into the arteries of the brain and many, many other things. See your doctor for a full evaluation.