Can it be Implantation bleeding?

So yesterday when I went to use the washroom I noticed that I had one dark brown spot I thought my period would come so I put on a pad and later noticed I only had another spot and thats all today nothing. I'm supposed to get my period next week on the 15th. I had no cramping only nausea and headaches with just wanting to eat sweet food. Me and my fiance been having unprotected sex using the pull out method so i know there may be a possibility I can be pregnant but we're not bringing our hopes up.😕