I had an abortion 4 Weeks ago and I waited about 2wks before having I've have sex with my husband about 7 times since and he pulls out every time, but my Sister said I can still get pregnant and Very easily even if its pre ***. Is that true and should I take a pregnancy test? Is it to late take a plan b. I mean how soon does my period start after having a abortion.. I'm confused now.

There is very little chance of sperm in pre-ejaculate, but that's not why so many women do get pregnant using withdrawal - it's because semen starts to come out just as he withdraws, and neither of you are aware of it.
There's no way to know when your cycle will start again after an abortion.
PLEASE get the pill or patch.