It sounds like you O'd on CD 20, So I don't think you BD'ed to late. You have a dip on CD23... which is too early for implantation... Implantaion dips occur after 7dpo. You ovulate 24-48 hours after your first + OPK. What time of day did you test when you got your +?
It sounds like you are doing everything you should be. I know it is hard not to stress about it and it all seems like it takes forever. But, from what you have told us you have BD'ed right when you should have

Good luck and I hope you get your BFP!!

Tanya