I Am Taking 1/35 Nortrel For Birth Control. I Just

I am taking 1/35 Nortrel for birth control. I just recently switched from my last birth control, which has less hormones, over to Nortrel. I just finished up my 3rd pack, and when it comes time for my period it is usually really light and only lasts a few days on Nortrel. But this month all I got was brown discharge and enough one day kinda blood/ kinda discharge to fill up a tampon. Is this normal on Nortrel and is it okay? Did I get my period or is that something else? Am I pregnant? I always use a condom along with Birth Control but I had sex earlier that month in the first few days after I started a new pack.