fiance dealing with ex wife

My fiance was previously married and have two kids. There has been so much going on with him and his ex wife. Fiance is stressed out and i know depression is hitting him..hes been very angry and quiet, i feel when i try to help him be happy its not working. All of this is also taking a toll on me... as drained as he feels i also feel so drained but i dont give up on trying to help him. I feel so lost and empty because hes been so different for the past two weeks but i still try to stay strong for him. With all of this i feel like im on the edge, i need to vent i need a shoulder i need help from someone who has experience. Ive tried talking to my married friends but they dont know what to really say and i totally understand. I just want to help him so much more but theres only so much i can do when it comes to him and the ex wife because their problems are not my business. I feel stuck and just lost.