I'm a 22 yo female and I've been suffering for 2 years with bad nausea regardless of what I eat or what time of day it is. Also, I sometimes have diarrhea and sometimes constipation which doctors interpret as IBS. I've had all kinds of test done-h. pylori, gastroscopy, all possible blood and stool tests... and they all came back fine! I've been diagnosed with anxiety and emetophobia and doctors try to convince me all the physical symptoms come from that but I can't believe it. I'm tired of living like this, If anyone's had similar experiences please share 
I'm desperate at this point because I can't do anything or go anywhere anymore, I feel worse than people with serious illnesses
Your symptoms comes and go or stay there all the time. Take Zantac and try to relax your self. It seems to me you get stress and anxiety disorder. Go to psychologist and talk to your best friend resolve the hidden issues. All the best.
When you have IBS, all your test results will come back clear because IBS is a functional disorder. I have had these symptoms too along with stomach pain and I was diagnosed with IBS too when all my tests were negative. Worry will make your symptoms worse and is a classic symptom of IBS.
I feel you! I'm 22 yr old female as well. This is Almost exactly what I'm experiencing.. I'm staring to think it's just stress/anxiety! Have you thought about going on benzodiazepines? Like a low dosage of Xanax or something.. I've noticed that I'm so spaced out on them I don't notice my stomach problems but I usually take a lot more than a low dosage. Feel free to message me if you think of any more symptoms your experiencing, I'll try to help you out best I can. Feel better!