Is purging without binging still an ed? Isit harmful to my health if I only do it 1-3 times a week?

YES. And yes! you have an eating disorder that requires expert intervention. Start with your doctor for general health assessment and referral.
Yes it is. Purging along with binging are all part of a eating disorder. I would strongly recommend that you discuss this with your primary care provider and consider getting expert help as it may cause significant problems in the long run. Eating disorders can cause significant health problems and need to be treated as soon as possible.