He had left at a bad time for you (that is not very supportive) yet, it is possible that he had just felt overwhelmed (and still loves you and is confusing his burned out feelings w that of being out of love)
The two of you have been together for quite some time. Try to find out if he would be willing to consider couples therapy.
Depression is very treatable condition. You may want to connect with a psychiatrist for medication (if you are not on any) and with a counselor. Your whole perception and energy level will change with the right treatment regime. Why let the depression ruin your life and rob your of someone good as he?