Implantion bleeding is usually just very light spotting, and only lasts a day or two at most. It is very different from a normal menstrual period, and it does not happen in all pregnancies.
If you think you may be pregnant, the only way to find out is to take a pregnancy test. Or wait nine months and see if a baby comes out. But really, the pregnancy test is a lot easier, to say nothing of quicker.
And of course, if you already know you're pregnant, and are experiencing strange bleeding, you should call your doctor.
"The only unnatural sexual act is that which you cannot perform."
-- Alfred Kinsey