Can Levonorgestrel Be Taken Again After 2 Days?

Hi, I took ecp (levonorgestrel) 2am on the 16th of feb and I have had to take them again today at 1am? 18th of feb.. Is it safe to use like this? How long diss it stay in your body for? Could I get pregnant still. I took both the pills with in half an hour of contraception failure.