which collar is it?
Does it allow the head to still tilt forward even if it is a little bit, and not stay centered on the spine?

Once things get settled down, does PT suggest going w/o collar for short periods of time to let muscles build back up slowly?

I don't know how long it is OK to wear something like that, if it is holding your neck / head up at some point seems like muscle tone will be lost.

Is the PT is monitoring and guiding you.

I'm sure with eds it is a delicate balancing act...