Hi, i've sucked 5 helium balloons and now i'm coughing and it hurts my throat i also hav a mild headache and a pain in my lower abdominal ?

Then stop: Inhaling helium displaces oxygen in your lungs and can cause a relative lack of oxygen to your brain (possibly causing the headache). I also assume you weren't sucking down "medical grade" helium and there may have been some contaminants in the helium balloons giving you a pneumonitis and brochospasm. If it continues then get medical attention ASAP.