Period for 3 days now spotting?

Ive always had a very predictable cycle. Always 5 days with 2 days of spotting lightly. Now, I started taking PreNatal vitamins last month, stopped taking allergy medication and well, that's it. My period started a day late, but the 3 days I had my "period" the bleeding was heavy. Then it just stopped out of nowhere and it's been light (very light and not the kind of spotting I'm used to) spotting for 3 days. The spotting is exactly what I had when I became pregnant with my first child. I had every symptom possible of being pregnant, now I'm left with just the fatigue, crazy allergies, and this random spotting.