Hmmm... I believe mine were injections for every three days, too, but, now that you mention it, I don't think they lasted for six weeks. Maybe three? *Sigh* I can't remember. This was almost a year ago now, with my boa.

In any case, yes, mind were injections and I was told to keep giving them until they were gone.

If symptoms persist after all your meds are used up, another trip to the vet is in order. The meds either weren't enough, or your snake has something other than an RI.