My 17 Year Old Daughter Keeps Telling Me That She

My 17 year old daughter keeps telling me that she has anxiety that comes on a few times a week with no rhyme or reason. It starts with her stomach cramping and goes to her throwing up. I thought it was school or mid terms or tests but it happens at odd times and no reason. School is out and no real stress from that. Not sure what to make of it but it is now keeping her away from friends and fun activties as she does not want to have to throw up in front of people or at a party.