Weird Period

So I started my period last night after i got out of work. I bled like normal, (usually somewhat heavy) but this morning I wasn't really bleeding at all. It was kind of like my period ended, when it gets darker in color and there's barely anything. Is this spotting? I've had protected sex before I started, and I'm just confused on why my body is doing this. Could anyone give me and ideas on what this is?