Vomitting, nausea, stomach pains, missed periods. Gastritis or pregnancy?

Hi.. Lately I ve been experiencing vommiting. Nausea and well stomach pains. I had a doctor s visit today and they took a urine test and it has been taken into a lab for more studies. Tomorrow I have another appointment. I m afraid that it might be gastritis or even pregnancy.. Due to the fact that my period has not came in 2 months. I m concerned because I have missed a month before and then continued on with my irregularities. But how can I be sure of what I m experiencing? I m extremely shy to talk to a doctor face to face about it.. But I m just really worried. I guess my question is, how do you differentiate gastritis and pregnancy?