I'm in a similar position as you are right now, only my cycle was a couple days early. And I've been doing a lot of reading on this kind of problem since then too.
I worried what I had was implantation bleeding as well, but from what I've read, such bleeding is incredibly light and is either brown or pink and only lasts maybe 1-2 days. So if there's been bright or dark red blood that lasted more than a couple days, it's most likely not from implantation. Also, an ectopic pregnancy would yield a positive pregnancy test; the pregnancy hormones would still be there, even if the embryo was developing in the wrong place.
How do the pains in your pelvis and back compare to your usual cramps, if you have any? Have they let up at all since they began?
It sounds like maybe the bleeding is coming to a stop, hence the pinkish color rather than the red. An abnormal pap exam result could have something to do with it; there are a couple of female conditions that can play tricks with your cycle, such as ovarian cysts and endometriosis (some women get symptoms, some do not). If you've done anything different in your life suddenly, like stressing, begun exercising, taking medication, moved to a new home, went on a new birth control, or lost or gained a lot of weight, these are all things that can contribute to a screwy period.
And honestly, it's sometimes not too out of the ordinary to just have an off cycle. Mine are often fairly regular, and just once in a great while, -boom- I get one that's early or a little lighter than usual. Then I'm okay again next month. If one month things are a little screwy, it could just mean your body is feeling a little weird for some reason or another and bled less, or didn't ovulate, or was just being moody.
I've personally not taken a pregnancy test to ease my own fears because I think, under my circumstances, pregnancy seems a bit far-fetched. Perhaps you could ask your doctor to perform a blood test to relax you about pregnancy, because blood tests are foolproof. And it's good you're going to see your doctor too; hopefully they can try and find out if there's an actual issue at hand, or if you're just having an off month and it's the exception rather than the rule.
Also re: pregnancy, this is not something you need to answer publicly, but do you have access to a vaginal speculum? If so, you can give yourself an exam with said tool and a mirror. If your cervix is not purplish in color, it means there is no pregnancy. For some reason, that part of the female body changes color during pregnancy.
Hope you can get the answers you seek.
Irregular bleeding, dont know whats going on!! 
