I Am 26 And Have Been On Birth Control Since

I am 26 and have been on birth control since 16. I have never missed a period. 3 or 4 months ago I started getting brownish discharge about the end of my 2nd week of birth control pills then goes away and I get my period after the 3rd week. This last month I had way more brown then normal went away but my period never came. I'm not pregnant but wondering if this could be something serious to get checked out because eventually I would like to have children