Two, months after miscarriage. Can u get implantation bleeding the day after sex?

Maybe. Yes, you can get pregnant 2 months after a miscarriage. You can have implantation bleeding around the time of implantation which may be 5-7 days after fertilization. But you will not have implantation the day after sex if that's when you got pregnant!
Unlikely. If you haven't had sex for 2 months, and then you have sex, and then the next day you have bleeding, that likely isn't implantation bleeding. Key word is 'likely.' anything is possible, but more likely the sex caused a disruption of your lining, you may have been about to have a bleed anyway.