Nausea during period....?

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I recently stopped birth control (Estelle 35-ED) after being on it for several years (with a couple of brief breaks during that time) and today I started my first period since coming off BC. It began with the usual cramping but has gradually turned into a feeling of nausea and general 'yuck' sensation in my stomach. My flow is light to normal and I've taken pain relief for the cramping. Never experienced this before. I was thinking it was just my IBS or something but now I'm not so sure. Any ideas? This has never happened before, I'm 24 yo cis-female, not sexually active if that makes any difference? And the whole reason I'm being so paranoid is that I have emetophobia (fear of vomiting) so any and all potential scenarios scare me :-/