Have no idea where I am in my cycle...

Brittany
On cycle day 15 I got a positive opk. Husband and I did the deed for a few days and then we waited for good news. At 12 dpo I had some very light spotting that was pinkish brown. This lasted for 3 days. I thought it might've been implantation bleeding. Took a hpt a day or two after the spotting stopped and got a bfn.  Today is cycle day 39 and 24dpo. Took another hpt and another negative. Help please? I don't track bbt and have no idea how to figure out where I am in my cycle, except to wait for AF to show up.