Hi, since your question is unclear, I am assuming that acv means apple cider vinegar. For that my opinion is - acv is assumed to be beneficial for weight loss. few articles about this suggests that its beneficial in diabetes,lowering cholesterol level, in acne prevention etc.the important thing to know here is acv, that to a tablet form is highly acidic which might have caused gastritis or ulcers which presents with nausea and vomiting. And as far as the headaches it might be because of altered blood sugar level which is due to the effect of acv on insulin.And coming to the pregnancy, if you are really concerned about it, you can do the urine pregnancy strip test in your home itself to ruleout that.So I advise you to stop taking acv immediately. And consult a physician for further management.