orthokeratology- ghosting

Contact whichever professional you got the lenses from, asap.

You can't get qualified advice on an online forum populated by a lor of teenagers. Your sight is too precious to not take seriously.

It is difficult to answer that question without the results of your fitting exam. If there is no astigmatism in your lenses prescription but there is some in your original prescription it can cause that, in addition small errors in BC fitting can cause that too. You should go back to your optometrist.

my optometrist says it's because of astigmatism because I have to wear the lenses for a few weeks, but I've had this ghosting for about 12 days and it doesn't seem to be decreasing

Go back to your optometrist. Sometimes it takes longer to work properly. Honestly, I think it is a bad fit, you need to be re-fitted probably with one with astigmatism correction or different BC.

Do you have experience with misight lenses from Coopervision? What do you think of them>

They don't work differently from OrthoK. While OrthoK works on flattening the curvature of the cornea to correct the eyesight and it's effect lasts for hours, misight lenses works on undercorrection for up close to avoid strain caused by strong minus lenses and to avoid lens induced (and strain induced) myopia progression. MiSight is sort of multifocal contact lenses.
In OrthoK you go lenses free for a day or even longer (I've heard about people who can go for 3 days without lenses after one night with OrthoK. With MiSight lenses you have to wear them during the day to correct your eyesight. The fitting is different and not everyone is suit to both methods.

I prefer MiSight because I am more familiar with it.
Both are not improving the eyesight but stabilizing it, this is a serious misconception about them.

Kathy, do you think the dk rating of MiSight lens or the infection rate with soft lenses is anything to worry about?

If the fitting is right and you use them correctly you have nothing to worry about. If you have seasonal allergies and infection you should take breaks from contacts during those days anyway.