Brown blood instead of period

So I’ve never had an irregular period. I went off birth control about 7 months ago so we could try and get pregnant. I originally went on it for painful periods, for what’s believed to be endomitriosis. Anyways, I got my period the expected day except I have had NO red blood yet. Only brown, and I got it on Tuesday. It hasn’t been super heavy, not enough to wear a tampon and I’m a little nervous. Has anyone else had this happen to them?