Could I be pregnant?......Need Advice QUICKLY PLEASEEEEE!!!?

Okay here's the story, I am currently taking Yasmin and there have been a few times that I have taken the pill a few hours later than what I usually do and one day I missed it completely. In January I was supposed to start my period on the 2nd but didn't start until the 11th. Once I started it was very light and a thick dark brown color blood?!. I took a pregnancy test during the time that I was late and it was negative. I was due to start my period again yesterday and have been cramping for the past week. Today, I noticed a thick white colored discharge. I've also been feeling a little nauseated and urinating quite often. I haven't taken another pregnancy test since the last negative one. Could I be pregnant? Or could the nausea and frequent urination just be from the birth control? Has anyone had similar experiences and then found out that they were pregnant? Any advice/suggestions are much appreciated. Oh and sorry about writing so much, I just wanted to be as detailed as possible.