birth control

I got birth control I believe on December 17 and I had sex the next day and my doctor said that I probably wouldn't get my period. I usually get my period in the first week of the month or maybe the first few days of the second week. I wasn't getting my period and so I thought oh I'm probably not getting it. So I didn't worry about it. I've been sick so I've been having stomach pain and nausea and I'm thinking maybe it's  because I'm sick and not eating well. I just went to the bathroom and found spottings of blood not sure if I'm starting my period or it's just that annoying spotting or? Can someone help.