Got period at 12dpo and faint positive? Help!

I got my period at 12dpo (yesterday). I wasn't expecting it for another 5 days (long luteal phase consistently). Was heavy and red so I am thinking it can't be implantation bleeding. I have had a cramp in my ovary for the past 4 days also.  Never get period cramps. It was so early that I took a pregnancy test and it was a very very faint positive! Could I have miscarried? Thoughts? Any help appreciated