Can implantation bleeding happen the same time your expecting your cycle?

I was curious to know can Implantation bleeding happen around the same time you would be getting your cycle.....Also I read up on IB and they were saying that its not heavy at all...I was askign around about it and several other people told me thats not true at all that they might have had some heavy bleeding at first....Im curious because Im not sure if I just had my period or if it was implanation bleeding because the first two days of my cycle were not heavy but not spotting and then i spotted for a couple more days. Im just thrown off because my cycle wasnt 7 days like it usually is it was only about 4-5 days the first two days it was almost as if it was normal and the last two days was spotty almost nothing...I started my cycle around the 31st of last month and ended around the 4th or 5th of this month..Today is the 17th and about a week ago I started to feel as if I was going to start my cycle again...except for my werent tender up until yesterday...Im confused because I havent been feeling exactly right but at the same time it happens time to time