I can't possibly know what is in your boyfriend's head, but he is exhibiting some classic signs of depression. First of all, being depressed makes it hard to find joy in anything, so that 'spark' he used to feel about you would naturally be hard to find if he is depressed. You may want to ask if he is finding a 'spark' in anything lately...this may help him decide whether it is really the relationship that is a problem, or just a manefestation of the depression. Also, many people when they are depressed isolate themselves, and may push friends and loved ones away. Has he distanced himself from other friends? Again, this may help you know if his behavior toward you is just the depression speaking.

You say that the two of you care very much about each other. Perhaps now is the time for you to be a friend more than a boyfriend. If he is depressed, seeking therapy would be a tremendous first step toward getting better. Perhaps you could help him find someone to talk to - he will have to take the step of going to see the person, but you as a friend can help with the up front work. Based on what he says, he may be having trouble feeling any kind of romantic or sexual feelings, so make sure he knows that you are there for him as a friend without expecting anything more until he is feeling more emotionally stable.

I will warn you - he may still try to push you away. I know I did that with many people when I was depressed. But I can also tell you that my most treasured friends are the people who stuck it out and remained my friends through all of my worst times.

Good luck, and let us know how you are doing.
mj