doctor

Is it normal for OB's to cancel appointments weeks in advance? mine has now made me reschedule 2 appts with no explanation and it's frustrating because my hubs and I have arranged our work schedules for the original appt. now the rescheduling is a problem because they can't fit me in! I work part time and so there are plenty of hours that I'm available, and they conveniently don't have any slots available outside my work schedule!!! I planned on changing doctors but wasn't sure if I was overreacting and this is a normal thing or if most people can count on their original appt date/time?