Trying birth control

Amanda
So I'm going to the Dominicans for my graduation trip next month and if my period comes a week late that month then I'd have it on the trip which I don't want. so my family doctor told me to take birth control pills everyday until I'm fine with my period coming. 
Yesterday I took my first pill while on my 4th day of my period and had intense cramps for the entire night so I decided to not take them today and start once my period finishes. Thoughts?