Also bear in mind depending what you take, I have been in situations that resulted in them having to order one or the other and I promptly put mt doctor in that loop so I always get mine 2 days early just in case, they do usually work with you really well once the flow gets going.
Good luck to ya
In some states there's some pharmacy rule/policy that says they can "fill 2 days early," so even though your pain doctor might see you every 4 weeks (for example, "Mondays"), you can get your script filled every 4 weeks.
Insurance has a mind of their own, though, so you may end up having to coordinate with your doctor to "match" the Insurance payment cycle.
Every state is different, and every insurance is different, so I'd start with a phone call to your pharmacist to find out their policy. Then, call your insurance/medicate, go over that with them.
THEN, after you made those calls, if everything is fine, leave it alone. But if it is not fine, then bring it up to your doc. (They'll work with you.)