When will I get my period if I have been off the depo for 4 months

It will vary from person to person. It may return next month, it may not be for several months still or longer.

It should show up within the next two months.

I tell my girls before I give them the depo shot that it should be considered long term birth control. It is not uncommon at all for it to take as long as 18 months (yes, that's a year and a half), for natural hormones to return to a normal level in order to ovulate, menstruate, and/or conceive.