[Lizzie]

There really isn't such thing as heavy implantation bleeding. It would be very light spotting and would not mimic a regular flow at all. That and the fact you got a negative pregnancy test should reassure you that you are most likely not pregnant.

But keep in mind for the future to use birth control, because semen can still leak out of his penis before he actually ejaculates, it's not a safe form of birth control in the least. Not to mention it does not protect you from possible STDs.