Hello, and "yes" it is very possible that ample time has not yet been given to have the antibiotic, really perform to it's fullest extent yet. So, I'd wait a few more days.
This what I would do: As mentioned, give it some more time. But, if it is not improving by the time another week goes by, I would then see another either the same, or another "ENDODONTIST". Why? 90% of all root canals
work well. About 10%, or so, do have secondary problems
. Your root canal, "could" be one of those in the 10%... Hopefully not, but given some time & taking the antibiotics - you should soon KNOW if you are either improving or not. If not, see a good Endodontist. As the root canal, "may" need additional assistance, such as an apicoectomy or retrograde filling, etc....
I hope this helps you. You are doing the right thing now, keep taking the antibiotics!
I hope you indeed get feeling better speedily!!!