I'm usually really regular with my period coming on the same day every month. For the past couple months it's been coming on the 18th. So today I was fully expecting my period but what I had was some light pink spotting this morning and then nothing until this evening when I had some brown spotting. Could this be implantation bleeding? I had a miscarriage last year and didn't even know I was pregnant, so I'm not really sure what this is.