Implantation?

Sooo didn’t have any sex this cycle until 4 DPO (we track with a variety of methods including bbt and LH strips so I’m positive about ovulation) so I feel like it’s not possibly to be pregnant but today I spotted before my period (expected tomorrow or the following day). I’m anxious that it was implantation bleeding. I’m 12 DPO, any thoughts? Don’t have a picture of the bleeding but it only made a tiny stain on my underwear and looked like the start of a period on toilet paper (red blood) but then stopped. Also wondering if it’s bleeding from having sex yesterday that was a bit intense. Help!