You can request them to change the appointment for you (by phone) or ask them what is the purpose of the coming appointment? You can skip once if you think it's not important!!!
Sorry arh, my Oct. BB will be my 1st baby (pls. amend it again)!!
I have the same experience as you, my tummy also feel painful sometimes, but the doctor said it's should be alright as the baby is growing up in yr tummy mah!!! :-P