Sitting cross-legged when learning deen due to difficulty

I attend Madrassah for a full day and often find it difficult to sit in the jalsa position for long periods as I start to experience hip and knee pain. I was told sitting cross legged imitates the kufaar and not good etiquette so I avoid sitting that way. I also don't like to lift one leg up as I feel it's disrespectful to have the knee above the desk where the Kitaabs and Quraan are.

What are some permissible ways to sit when acquiring deeni knowledge, this applies to even attending taleem and other programs besides Madrassah... and also, is it permissible for me to use a pillow under my hip (not for salaah) but in a program or in Madrassah?