Eleven months ago I ended up taking 3 weeks off work whilst I overcame abdominal pain. After ultrasound and H. pylori tests, a good response to Omeprazole convinced my doctor that I had 'functional dyspepsia'. Basically too much stomach acid for no obvious cause. Usually stress induced. After another couple of months I gradually came off the Omeprazole and was fine until 6 days ago.
I recognised the pain straight off and took Omeprazole to allow me to sleep through the night. The doctor reckons I'm in the same position again - probably due to student finals exams approaching again. I sometimes think it would be easier, and less stressful, to retake them rather than help in running them!
Last year I had to stop running for a few weeks and lost fitness when I restarted as uphill running was uncomfortable. I'm assuming that this was due to increased abdominal pressure needed to maintain core stability. After the gains I've made in the last few months I really hope I'm not back in that position once again.