ADD Medication

I'm not sure if Concerta is working for me? I'm a 20 year old female and I was recently diagnosed with ADD. I was prescribed with 18mg of Concerta, once every morning. I didn't feel particularly focused, but I suppose less distracted than usual. I felt very calm and relaxed on the first day. But since the first day, I don't notice any difference at all.

A couple days before starting Concerta, I started to have abnormally intense hunger pangs to the point where my stomach would start growling every two hours if I didn't eat something. Even after starting Concerta, the hunger hasn't gone away but now I feel nauseous all day long. I'm having rather frequent BMs with occasional diarrhea. I also have really intense headaches (hydration doesn't help; I drink 8-10 glasses of water a day). And I'm not sure if this is normal, but I've noticed a definite drop in my motivation to do anything. I have some heart palpitations from time to time (PVC), I'm guessing that it's a result of taking stimulants; but no trouble sleeping.

Is this normal? Or should I ask my psychiatrist to switch to a different ADD medication?