Definitely stuck shed if its been that long. This is most likely due to stress or humidity issues, though I'm leaning towards humidity issues more because you have stated that your humidity is a bit unstable.
My bp shed right away ( a day after) after clearing up from the blue.
What you need to do is soak your bp in shallow room temperature water for an hour then run him/her through a damp towel and just help the shed come off basically. You need to get this fixed right away as stuck shed can lead to some blood flow issues , etc.
In the future to keep your humidity stable. Avoid heat lamps for heat as they dry out the air and put some sphagnum moss around the enclosure and mist those a bit. This should keep humidity up.