What Causes Irregular Spotting Instead Of Periods While On Birth Control Pill?

I had sex for the first time with my boyfriend on March 27th, then again on March 28th, and on April 4th. I am on the birth control pill, Falmina. Each time we had sex we used a condom and he never finished inside me. Sorry to be graphic but we would start with other things other than sex..basically I gave him a blowjob and he came in my mouth, then a minute later he put a condom on and we had sex, and like I said he never finished again inside me and that is how it would go each time we did it. The reason I m asking is because this is the week I normally get my period, it usually comes on Wednesday which is today. Monday when I wiped after going to the bathroom there was a little tiny pink color. Then Tuesday there was a tiny tiny light brown discharge in my underwear but it was barely noticeable. Then later that morning there was a little bit of red blood in my underwear so I put a pad on. As the day went on I kept getting some red but then it was a lot of light brownish color and some clotting it seemed like. Then other times that day it was darker brown. Today, Wednesday, when I normally first get my period, there was nothing in my underwear. But a little later in the morning I started bleeding on the pad I was wearing and it was just red blood. I went to the bathroom and blood was dripping into the toilet so I wore a tampon and pad the rest of today. I changed my tampon and there was quite a bit of red blood on it and in my pad some darker red. Then later that day I took my tampon out but there was not a lot of blood. Now I ve been wearing a pad and there s no bleeding at all. This is very weird for me because I usually have heavier bleeding on this day and it progresses. I m very confused and nervous something is wrong because I had sex and I don t want to be pregnant. What are the chances and why is this happening?