Pills, Missed Period

I've been on the pill since January, and every month during the allotted week, my period would come for 4 days. In June, my period didn't come but I had some really light sparse brown flaky discharge during that week. I took a pregnancy test during that week and it was negative. Is there any way I could still be pregnant? Did I miss something? Are these symptoms concurrent with pregnancy? I appreciate any information I can get. Thanks!