The morning after pill basically screws up your system extremely badly, which is what causes the heavy bleeding and nausea. It's like taking an extra triple quadruple dose of the stuff that is in the pill.
You'll have to wait at least a cycle or 2 before it all gets back to normal. That's the price you have to pay for taking the morning after pill. Sure it works great, but the problem is that it makes most women who take it really, really sick and they also have a lot of issues with bleeding and other stuff after taking it. You just have to give it a few cycles to let your system get back to normal.
I used the morning after pill OFTEN in the last 6 months and i found that it did bring my period on a lot sooner but i made sure to eat a good amount before it took it and to keep food in my system. I've heard horror stories like that from people who take it without food.
I took more then one morning after pill during a weeks time w/ no bad side effects at all (only light cramping now and then) until about a week after my period. lots of pain in the pelvic area etc, (dr's found a cyst, see other post), I'm thinking maybe the pills aggrevated it, not sure though. In any case I did get my period as normal afterwards, but my next one I got 11 days earlier then I was supposed and it's a very light period. Until these last two periods I've always had extreme cramps that leave me crying it the tub all day, but it seems the pills have gotten rid of my cramps, no pain at all, at least temporarily. I guess they work different for different ppl. Weird.