mayb hes bipolar lol! explain that u dont feel comfortable practicing infront of him and that you dont want to b embarrassed. he probably took it the wrong way and kinda got hurt. never assume always communicate. why should he ask u why u dont want to or how it makes u feel...tell him. sometimes you gotta stop expecting things from people and just ask them and be upfront about things.

in all it seems like hes a good person. good luck!