Can I just add don't take a double dose, it won't work. Birth control pills work by maintaining a low 'noise' level of oestrogens, higher than you bodies natural level. This is to stop your natural variations in oestrogen levels.
http://www.womentowomen.com/images/m...cle_060809.gif
(it's down the bottom notice how it rises and dips, the high level stimulates the release of Follicle Stimulating Hormone- FHS and luteinizing hormone - LH which equal ovulation)
In a natural cycle in dips low then skyrockets to induce ovulation, the continuous level dose prevents the raising of oestrogens in this way. Seems a little counterintuitive but it works.
It's the black line on here, the red being the 'normal' cycle oestrogen levels
http://www.contraceptiononline.org/s...22_s010_lg.gif
So you see taking two will not really help, they probably made you sick because the oestrogen or progesterone doses was too high.
On a side note and for completions sake the progesterone in contraceptive pills is there to mimic pregnancy, thicken cervical mucus ect. Basically you can’t get pregnant if you already are/ your body thinks you are.
Good luck to you, hopefully you have gotten away with it. Remember stress can delay periods so try not to think too much about it.
EDIT - before someone sciency tells me off - this is just a basic idea of how they work, other things are involved as well