TMI moment, but need advice


So I've recently started walking and I started my mile week this week. I went for my walk yesterday, got home, showered, then went to the movies with my man. I went to the bathroom after the movie and found some light spotting, but the color was a bit off. This morning, I found that I had started what I thought to be my period.

As normal, pad, then go to work. I went to change my pad at work today and found a black, almost tar like substance that smells weird... Not period blood smell in place of the blood. If this makes any sense, there was blood IN the pad, but this black tar sitting on top. I'm honestly a bit freaked out about this and I have no idea what is going on. I've read so many things on line about this, but none of them seem to add up on symptoms.

I completely skipped PMS this week, didn't get emotional about anything and didn't have my normal monthly cravings. The discharge (not sure what else to call it right now) started 4 days before my expected period. It is thick, black, and smells funny. I am not having any cramps, which normally I am in nearly crippling pain my first day, and the actual bleeding is very minimal.

Anyone have any ideas??? Has anyone had this happen before??? I'm very clean down there, and no STDs. I am sexually active, but the last time we did anything was before my last period.

Should I just wait to see if anything else develops or if this continues for longer than my normal period?