Hello, I'm totally new to this forum. 

I've been mewing (or at least trying) for almost a year and am primarily focusing on tongue posture. I don't do any additional chewing because I feel my bite is (temporarily) changing when I do so. Normally, when I emphasize on proper tongue posture, my bite is pretty normal with the upper incisors in front of the lower incisors. After a while chewing though, my whole mandible seems to shift forwards causing my bite not to close properly anymore - my incisors then sit on top of each other or my lower ones even exceed the upper ones (slight underbite). This effect wears off after a few hours to a day after quitting chewing. The more I chew and pump my masseter muscles, the more my mandible is shifted forwards causing a slight underbite. On the other hand, the more I push my tongue against the palate, the better my bite feels (more overall tooth space), this is why I only focus on tongue posture/ strength atm.

Does or did any of you experience similar issues and if so, knows a solution to this? This problem has kept me from doing any chewing besides from food. 

Thanks in advance.