help me out ladies

Okay so I'm very regular I always start on the 15th every month: last month I started on the 7th for no reason. My period ended on the 11th (keeping with my typical 4 day period) I did several hpt so ensure it wasn't implantation and even had bloom work done everything negative. Now it's the 7th of December and I have no clue when to expect my period or when I may have ovulated. This was the first month we didn't focus on it and really try to conceive any ideas when I might start this month? No period like symptoms other than a very small amount of random cramping and today I had a few drops of pink blood when I wiped and then it was as gone.