What is it with maternity jeans!

I am trying to find some casual blue jeans. I have tried maternity jeans at boohoo and River Island (where I normally get my jeans). I don't know if it's just me or the fit but they feel so low down at the back, like I have a really saggy bum lol and the front doesn't feel high enough either... Does anyone know any places to get jeans, any tips welcome?