Lila - Check and see what your GP says, but if the chemist have labelled the pack as twice a week that would seem reasonable. However Cubagirl has also looked and it says once a week. Check with your GP, rang and ask / insist to speak to him / her to clarify.
When you say the patch is coming off in the corner, is it just lifting at the edges or is it actually lifiting off. I find it really helps not to use any moisturising shower gels as they make it more difficult for patches to stick.
You say that you have seen that there are only two types of patches, but you have seen more. I think there are only two of the conti type patches but there are more of other types of patches, but they are not conti - combined oestrogen and preogesterone.