The flame has died and was doused in water

I have been with my current boyfriend for 3 years now and we have been living with one another for 1 1/2. When I first met him things couldn't possibly be better. Without going into great detail we had a pretty active sex life, he was very romantic and attentive and he was so happy all of the time it was almost infectious. His father passed away a couple of years before we met, so there were the occasional weekends or holidays where he would be withdrawn and quiet, but that was expected and I understood. After we moved in together his periods of depression lengthened and got even worse. He wasn't interested in spending time with me and things he would have previously been happy to help me with made him act put-upon and inconvenienced (I had a cat with kidney disease at the time that needed regular medication and fluid administration every day and it would make him angry because it wasn't his cat.). To top it all off he wasn't interested in being romantic any more, he started ignoring me in favor of video games or naps. We have had SEVERAL conversations regarding his depression and he doesn't want to talk to anyone because he feels they wouldn't understand him. He will try supplements and exercise for a week or two at a time then give up. The only physical contact he has given me in a year is to either grope at my breasts or my butt, and that just doesn't fly with me at all, if you want me, you want all of me or nothing at all. I'm at the end of my rope here. I still get virtually no help around the apartment as far as keeping it clean or caring for the animals, and now my Grandmother is in the hospital so much of my time is split between work and being with her. I don't know what else to do. I don't want to abandon him to his depression, but he is slowly taking me down with him. I'm interested in anyone's advice, but especially curious to see how guys think I should proceed...

im a guy and this is wwhat i would do i would have serious talk with him and if that doesn't work i would talk to your doctor and ask whet he recomends for a good phyciatrist and make him an appointment and make him go if all that doesen't work that is when i would leave but not angerly and tell him if he truly loves you he should get help and once he cleaned his life up to come and find you buts thats just me