It's abit early for implantation bleeding, that would normally occur closer to when u expect ur next period as the egg needs to be fertilised and make its way to the uterus and usualy takes 8-10 days from ovulation.
The spotting could be from all the bding, I wouldn't worry at this stage. Good luck :)
to be honest we dont BD that much maybe twice a week now!
Highly doubtful in my non professional opinion. I had implantation cramping and spotting that started 10 DPO. The spotting actually happened 10, 12, 13, and 14 DPO. I had slow rising HcG too. My pregnancy ended in missed miscarriage at 7 weeks:(
I've read some info saying the fertilised egg can take 3 days to travel drown to the Fallopian tube to begin implantation so you never know!! I wouldn't say it's likely or unlikely as everyone's body is different. You know your body better =)