Hi I Was On The Pill Yasmin Had Only Been

Hi I was on the pill Yasmin had only been taking it for 3 days and was then sick due to catching a bug. I didn't take another pill or carry on with the packet. I had a withdrawal bleed which was very uncomfortable because I had only just had a period a week before. Since the withdrawal bleed finnished I have been getting this brown paste like discharge in my underwear. Is this due to having a withdrawal bleed? Could it be something serious?