Masturbation and depression

I'm a 50 year old male with no relationship and chronic depression. My libido has been decreasing steadily over the last few years. Five years ago, I experienced sexual frustration that motivated me to masturbate once or twice a week. Now it is depression and emptiness that motivates me to masturbate. Usually I have no desire, and I just feel nothing from looking at arousing videos. But if I persevere, eventually I start to feel mild arousal and I waste a few hours. I usually don't have an orgasm; I just get tired and give up. Ironically, I waste more time masturbating now than I did when my libido was higher. I have back and neck problems, and the masturbation aggravates them. Plus it is such a waste of my life. Unfortunately whenever I decide to give up masturbation, the depression gets oppressive. I spend a lot of time staring into space thinking about how meaningless and humiliating my life has been when I should be working. I don't know if this is withdrawal from an addiction, or if it is the baseline of my depression without the medicine of masturbation. The feeling of emptiness is not related to loneliness or lack of things to do. I experience it at work surrounded by coworkers. Everybody seems to be only pretending to be friendly when they are actually repulsed by me. I just feel like I want to be a hermit so that people won't be constantly disgusted with me.

I appreciate any thoughts or advice.

EDIT: Another data point is that when I spontaneously decided to abstain from masturbation in 2009, I became psychotic two weeks later. Maybe it was a coincidence, but I often wonder if the chemicals in sex are connected to my psychological problems. I wasn't aware of being particularly sexually frustrated before it happened, but still I wonder if it somehow triggered psychosis.

Also, I don't take any medications. I have never had a very high libido, but age is making it even lower.

Sounds like maybe the baseline of depression without that distraction. I have bipolar 2 and wasn't feeling too well around last year -- depression, anxiety, hypomania...I was a 9 year smoker and I always looked forward to going outside for a cigarette, especially when I was alone with those difficult feelings. I quit about a year ago, but when I did, all the symptoms of my disorder felt much stronger. I realized that smoking was masking how bad the bipolar had gotten.

The thing is that where I really notice the difference is the following day while working. I'm not sexually frustrated, but I feel much more depressed when I abstain. I suspect there is some chemical released during arousal that I lack in my brain, and that chemical lingers for a day or so after arousal. That is my crazy theory.

That's probably part of it. I know for me the chemical was nicotine. Hope you feel better

I do feel better today, thanks My depression is weird, because it comes and goes every few days. When I'm depressed, I can't remember feeling any other way and I think it will last forever, but then it goes away and I remember that it cycles. Such a relief when it goes.