T.A.
A.,
Depending on how long he hasn't been able to eat and how his other "Activities of Daily Living" (bathing, brushing his teeth and hair, puttingon clean clothes, etc) are affected, it sounds like he may need hospitalization.
Depression that keeps him from eating is very serious.
I know he doesn't have insurance, but Capital Health at Mercer is a place to start because they have a program that pays for hospital stays when the patient can't.
There are also a good variety of antidepressant medication he can take since Lexapro isn't working for him. Wellbutrin is generally well tolerated by most and has good effects. Also, many antiseizure medicine can stabilize moods. One of those may work. Please don't stop trying with one medication. I can take time to find one that works for your fiancee.
If you ever think he's depressed enough to do something drastic, don't hesitate, don't wait, just call 911. If he talks about having a plan, get him to an emergency room. If he suddenly seems happy or relieved, DROP EVERYTHING and get him to an emergency room. That can mean he's decided to take action and harm himself.
This is also a very hard time for you too, A.. Please take care of you. He needs your help and support and you need to care for yourself so you can care for him.
Good luck and God Bless You.