Not sure if prego or still coming off cigarettes

Okay! So I need some advice so my period starts every 28 days or so. I started April 25th -28th. It was a usual period then on the 10th I spotted brown and red for a couple of days mild cramps then it ended. That's abnormal I've been so tired all the time but I also quit smoking two weeks ago on the 21st I'm now a few days late on my period I'm super emotionally sensitive randomly and some times get light headed other than that nothing else.