oh you sound like you are in a very rough spot.. I am so sorry for this..

The best thing to do, is to tell them to keep you out of the middle.. You love them both, but are no capable of being in the middle cause it is tearing you apart, and you can not hanlde it..

You want to be there for them both but can not do it anymore if they keep putting you in the middle..
I have been there in your shoes and it is not a nice thing.