Heavy cm, what's going on??

I started taking birth control sunday December 7th. The second to last day of the last period I had. Last night I didn't take my birth control. Same with tonight. I can't take it due to it causing other issues which is a long story. Anyway, all of today I had brown spotting. Very light. Then progressively a little dark red would show wi th the brown. I'm also having extremely thick cervical mucus. I've never had it so thick. It's brown and very gooey and sometimes comes out as a brown clump of mucus. What is this, and what is going on??