This is normal...
You typically should not just "stop" taking the pill mid cycle as the pill is a hormone supplement that tells your body not to release an egg or 'tricks' your body into thinking you are already pregnant depeidnig on they type of birth control you use.
When you take the pill as normal, the last week of pills (often a different color than the rest) are a placebo- or a sugar pill; they contain no hormone which then tells your body that there is no baby inside and it is safe to go ahead and shed the 'fluff stuff' that builds all month in your uterus.
When you stop taking your pill, the hormone stops and similar to the placebo pill effect, your body thinks it is safe to go ahead and shed - which is why you got your period "early" - but according to your hormone dosage (which is non if you stop taking the pill) your period is on schedule.
The reason you could be experienceing a heavy period is simply because your body is not used to such a drastic hormonal change. Many pill types start off with a low hormone the first week, then heavier the 2nd week and change again in week 3 so by stopping your pill mid-way you've simply confused your body.
Put your worries to rest though, this will not harm you or your ability to conceive. You may bleed again when it is your "normal" period time and may experience very irregular blood flow for the next couple months until everything is "normal" again.
If you are like me- your period may stop all together (therefore indicating that you are PREGGERS!!!)
@}~>~~