What Causes Brown Discharge During Periods?

I am 26yrs old and no medical insurance at the moment (in the process in applying for a different affordable insurance) that's why I came on here for advice. On April 8th I started my period and it was an unusual brownish color at the beginning and very little. I was sort of scared at the beginning but 2 days later my flow was normal red. Let me tell you before anything I always miss pills but usually double it up with no problem. On April 17th of course my period had just finished by this time I left out of town and kept forgetting to take my pills. No sex during this duration. I came back from being out of town on April 22. Upon returning I missed like 3 days prior and I had sex on the 23rd of April. As soon as I remembered I doubled up on my dosage, but I realized I started bleeding like a normal period this is only a week after my last. I am scared because this has never happened to me even when I have missed pills. Can someone please help me? I have done so much research but I am getting confused. Please help me. Should I continue taking my pills but I am still on the active pills?