Amanda,
your trainers do not siut your feet. You can take them back to the shop you purchased them from. i had exactly the same problam. I tried different socks, losening the laces and none of it worked. After about two month i took them back to the shop and they happily exchanged them. they said that they just didn't suit my feet otr the way i ran. Not every runner runs the same, some take long strides,n i personally take shorter strides. i tend to land slightly to the side of my feet, some people land neatly on to their heel first.
Take the shoes back. If it is a decent shop (normally owners are runners themselves) they will take them back, and allow you to swap. Test them out as well. go for a run around the block before you buy them. Good luck