Please help...getting frustrated...?

I have this really cute pair of hollister laguna skinny jeans. They are dark wash and I usually pair them up with some chestnut uggs which I tuck the jeans into. Anyway, I wanted to know something about the sizing. When I pull them on, it takes me at least five to ten minutes to get them and the crotch all the way up. They're skintight, at least, but then they feel like there sliding down as the day goes on. I mean, I love how tight and sleek they look on my legs, but I have a hard time wearing them to school cause I always have to pull them up. It just seems like every ten minutes, I have to put both hands back, flip up the bottom of the cami, wrap my fingers around the belt loops, and pull as hard as I can. Why are they so hard and tight to get on, but then they feel like they're sliding down? Oh, and I tried going up a size, but that just made the sliding worse, and I can't go down a size cause they would just be skin then lol. Oh, and I pointed out that I've tried a belt, so don't bother pointing that out.