Well I'm just going to start by saying that I got my last period on Sept. 20th. I had intercourse with my boyfriend on the 4th and then on the 8th. My period is usually regular. But on the 9th I had a little bit of brown spotting and then it turned into heavy bleeding like a normal period. It lasted about 5 days. It was heavy enough to wear numerous pads. I haven't had any pregnancy symptoms. Is this implantation bleeding or my period?

Sounds more like an off period. If women notice implantation bleeding, and most do not, it tends to be more spotting and of a short duration.
You could try a pregnancy test for the peace of mind, or wait until November and see what happens when your period is due.

The bleeding finished 2 days ago but it started again and heavy. Is that normal? Can a period stop and then continue?

Periods can do odd things sometimes... but it is also possible you are having some bleeding due to other reasons, such as uterine polyps. If it continues, have your doctor check things out.