Could stress/depression contribute to a low sex drive...my fiance will not have sex with me?

YES, most definitely BOTH stress & depression can lead to a lack of sex drive. The GOOD thing about it is that it CAN be taken care of IF he'll just do something about it. Simply ask him to PLEASE make an apt. with your family Dr. There ARE meds. out there that would "fix" both his situations & bring him back to normal again. I am on depression meds. myself & KNOW how well they do work. He also can get a med. for his stress. I dare say the Dr. may even give him sample meds. to take home with him, but I do KNOW for sure he would get scrips for both situations. The worst & hardest part is getting a man to go to the Dr. We females think nothing about going to our family Dr. for whatever the need/needs may be. For some odd reason a lot of men are not the same as we are. But I dare say that IF he'll go to just your family Dr. he will be back to himself in no time at all. Maybe even you could make an apt. for him IF it didn't start World War III. I KNOW without a doubt his problems CAN be taken care of tho, just get him there...all the best to you...:)