Are you on any type of BC? I know I get funky bleeding patterns whenever iI have sex with my guy, and maybe that could be it....but if you really are worried, maybe a HPT can ease your fears, but even then, you may just want to call your Dr's office and ask to talk to the nurse over the phone- they can make a note in your chart that you called and are worried about it. Just some thoughts, and I hope everything turns out ok :)
It is not normal to bleed like that after sex. It sounds like you may have an infection that requires treatment. This would not be implantation bleeding as it cannot happen that early (generally 7 days from intercourse at the earliest). That isn't to say that if you've been having unsafe sex that you won't get pregnant, but it would not be related to your bleeding. Get it checked out asap so you don't put future fertility at risk.