I think your cheeks will thicken up as you grow them longer. You should give them more time than 7 weeks though -- 12 would be better. I agree with Bearded1, your cheeks would stand out more if they weren't so dwarfed by the rest of your beard. Plus close-up photos always make a beard look thinner and more flawed than it actually is. I'm sure your beard is still maturing. My own stache and soul patch took much longer than the rest of my beard to fully mature. They only started to thicken when I was around 27 or so, and have only recently come into their fully mature state. Neither is as full or connected as I'd like, but no beard is perfect. I can live with that.

You already have an amazing beard as is . . . don't worry about it so much.