mask and image tracking

Hi, I'm pretty new to after affects and have been using the mask tracking features, and for my project i am putting a image behind a tracked mask so it shows the image over the video but im having trouble with tracking the image with the mask(the image kind of moves away while the mask stays where it needs to be). how do I track the image with the mask. I have tried using a null object and linking it with the image while having the mask path pasted on the null image and I have tried linking the position of the image to the mask and nothing works