I made the mistake of taking Hair,Skin,and Nail vitamins?

On Sunday I started taking a Hair,Skin, and Nails vitamin because I have some pretty bad acne etc. In this vitamin it is mostly vitamin A. My regular menstruation is further into the month, as in around the 15-20th is when it starts. But i got mine on Tuesday, and it was dark brown and a little pink. But it only lasted until Tuesday night and now im just finding a few spots of brown in my undies. Its Friday now. SOOOO I believed that i might be pregnant even though i took a test and it came back negative. I did some research and it said Vitamin A can cause menstrual irregularity, BUT could it cause my period to come early and to spot brown? Im really just trying to figure out whats going on because ive been feeling pukey since last week as well. Thank you for any info!