Vomiting, no missed period though

So, I had to take plan B 2 months ago and since then my period comes a week later than it used to. I got my period 2 days ago and it was unusually heavy. My boyfriend and I had unprotected sex during the first 2 days of my period and once a week prior (withdrawal method)

He did not ejaculate in me....

However, my period is unusually light today, as if it could be spotting, and it's only the 3rd day of my period.

I take medications on a daily basis (lamictal, vyvanse, and tritillex) but as of lately my schedule has been thrown off and I haven't been taking it as regularly as I should. The medicine makes me a bit lightheaded and sometimes nauseous... however I woke up about noon today, took my medicine, and an hour late I vomited all over my boyfriend's floor.

Im concerned if I should take a pregnancy test.