What is the packaging the product comes in? Is it discreet packaging?

The shorts themselves are in a clear bag and that normally comes in an Amazon bag or box. Until you open the Amazon packaging it's discreet.

When will the mediums be back in stock??

We re-made and stocked at the beginning of October, it is estimated that the end of October or early November there are goods, thank you for your questions, wish you a happy life

Do these run small? I usually take a large is lingerie panties but a small in yoga pants?

These in my opinion run a little on the bigger size. I ordered a medium which is my regular size but it was actually decently loose fitting on me. I would say size down but you can always get your regular size and do a return if it isn’t right.

Is it stretchy? i'm 5'8" and am probably around 170-175lbs. i wear a 10-11 in pants normally. torn between getting a medium or large.

Yes it is stretchy and the thigh straps are adjustable as well. The only thing I don't like is the band is thick and snug, but I don't have much of a waist though.