Is it safe to take plan b twice in one week after 72 hours? i missed my pills last friday and start again to catch up by taking 2 pills a day on weds

Yes, but...: It is safe, but not ideal. And you will need to use backup protection until you get a period and are totally back on track on your pills. I would recommend pregnancy before starting next pack. And it sounds like maybe pills aren't the best option for you - talk to,your doctor about different birth control options that you won't forget to take!