Am I liable for stolen money?

I work at an under the table job where they pay cash and never asked for any documentation. I've kept every work stub for taxes purposes. For a few months I've been doing the owner the favor of holding envelopes of cash for them. A few weeks ago, three envelopes went missing at my place of work (i had them all that morning & 3 were gone at closing) I work at a kiosk & that day there was a new girl. They are deducting the missing form my "cash envelopes of pay" & asking me to pay it all, & on top of that they wont give me a receipt, nor have they paid me OT this whole time. What should I do?