"Left feeling worried about my treatment working"

I am currently on month 2 of treatment and receive enough medication for 4 weeks until my next appointment. I normally book my next appointment on the day however I was unable to do this at my September appointment and was told by a staff member that I would receive my apt in the post. I informed her when this would need to be by so I would have enough tablets. She confirmed this would be in 4 weeks time. I then yesterday received my appointment letter for a week later than that, which I assumed to be a mistake as this would leave me with no medication for one whole week. There was also no information on my letter referring to any break in medication suggestions etc. I called up and was informed by the receptionist that this was correct, there was no appointments, and I would have to wait an extra week. I asked about an earlier date and was again told no appointments at all. I asked about cancellations and was told any cancellations would not be filled as they are already over the appointments they should have. I said again I then don't have enough medication and was told I can come off the medication for a week as it stays in my system for a week. I am very concerned that I am being left a week without medication and concerned that this information to stop my medication wasn't coming from a doctor, a pharmacist or nurse practitioners advice to me. I am concerned also the impact this break in medication will have on my progress and my side effects. This has left me feeling worried about my treatment working and anxious that I wont be able to progress up doses as planned.