Hi, not exactly the same situation but the last couple of weeks i was worried i was pregnant due to my period being 2 weeks late. I took 4 pregnancy tests, all negative.
I wouldnt worry too much, i worried far too much and i think this delayed my period too much. The 4th test i think confirmed my belief that i wasnt pregnant and 2 days later i got my period (yesterday) unexpected. I just stopped thinking about it, and it took me by suprise! I have just started Cerazette and it's quite normal for it to stop your periods. I dont think your upset stomach necessarily means you're pregnant. I have had a funny stomach for weeks, its generally anxiety i think.
If you're worried, take a test, but im sure you'll be fine. Its always best to double up and use condoms if you're worried as it will lessen your worry. I would see your doctor though, thats what they're there for. If you just sit and worry your stomach problem will only get worse and you will just get more worried and worried.
I was in this situation and it was awful, but now i know im not pregnant i feel silly for worrying so much. What will be will be. You'll be fine.