this same thing happened to me. I could hide my panic/anxiety disorder well and found it hard to cry for a long time because i was so numb. I lost lots of weight and everyone started questioning and even accused me of having an eating disorder. I was nauseous a lot and actually tried to gain weight but couldn't. i knew something was very wrong when my stomach was hurting every day all day long. it still does 6 years later. i was diagnosed with severe reflux. i went to a kinesiologist (sp?) and at the end of the appointment, asked him to take my blood pressure. He told me is assistant would do it.
After he went to his car, his assistant took my blood pressure and then ran back to the car to get him. He came back in and told my blood pressure was low--even for low. he told me to go to the emergency room but It was my mother's birthday that night so i didn't go. We went to a restaurant and i tried all night not to pass out.
It turned out that i was diagnosed a few months later with severe food allergies. they can make you lose weight, feel anxious, and have low blood pressure. also, it can make your stomach hurt. i think that is why i have reflux AND i think panic disorder caused it.