Is pregnancy likely after period, just stopped BC pill ?

The first day of my last period was 7/31 it lasted about four days. It was my last cycle coming off the pill. I had unproteced with my husband - we have just begun trying to have a baby, on August 7. Now on Aug. 13th I had a small amount of bleeding this morning which was mixed with a bit of cervical mucus. I havn't had anymore since then, I also have very mild cramp like feelings. Is this most likley breakthrough bleeding since this is my first cycle off the pill or could I have really gotten pregnant that soon after the end of my period and this is implantation bleeding ? Any thoughts or input would be helpful. - Thank you !