Implantation bleeding..? Could I be pregnant? HELP.?

My next expected period is in the next week or so. Based on my CM, I think I ovulated between the 1st and 4th of Dec. I had unprotected on the 28th (Nov) and the 2nd and 4th (Dec). On the 6th, I started spotting. It was very light and a brown color with a hint of red. It was mixed in with normal discharge as there was an abundance of clear sticky mucus. I only had it when I wiped that once and then it went away, only to happen again the following day. This has continued off and on for 6 days (today being the 6th day), progressing from brown/light red to just brown to pink. It has been very light though and only happens every now and then, sometimes I go more than 24 hours without any of the abnormal coloring. Instead, I will just get normal discharge, either creamy or sticky. It is not like a normal period at all, rather it feels and smells like CM. Since the spotting, I have had mild headaches, nausea, dizziness, extreme fatigue, lower backaches, dull twinges of pain in my lower abdomen, and swollen, tender, tingly ...could I be pregnant, and could this be implantation bleeding?