what if you are in chapter 13 bankruptcy and you are 4 months behind on your rent what happes to your case

Well, nothing should happen to your bankruptcy case, but your landlord will have the ability to evict you and you will be responsible for any unpaid rent that accrued after your bankruptcy case was filed. Depending on why you filed Ch. 13 to begin with and whether you are eligible, you may want to consider converting to Chapter 7 to deal with the debt to your landlord (if you plan to vacate). You should discuss this with your/a bankruptcy attorney in your area.