What can happen if you stop taking contraceptive pills during a week?

It depends on the pill; read the label's instructions on what to do for missed pills.

If you just missed a couple of days, you may be able to catch up again. If you missed an entire week, you might need to use other forms of contraception and start fresh with a new pack next month.

(Save that half-pack, though, for those emergencies when you accidentally run out and need pills to tide you over until you can get to the pharmacy.)