When I initially tried borax, I began taking 1/4 teaspoon per day and after a few days my testicles started to feel sore. I quit the borax instantly upon noticing that. I may fool around with health and life, but I don't want to mess up a good thing, so I am extra careful with my male parts. Anyhow I now take about a 1/16th of a teaspoon of borax mixed in my coffee about every third or fourth day or so.
I'm 45 and have been told that I have too much libido by my wife. I don't think so, but we disagree on that. She didn't begin this complaining until after we were married about a month. The timing of it all resembles a bait and switch ploy.
A couple of other things I have tried that seemed to have an effect on my testicular function, besides Borax, and Iodine, are D-Aspartic Acid, and Macuna Puriens(L-Dopa). You might try playing with them, and see if they help. It sounds like you couldn't hurt your libido right now, if it is non-existant. It may be worth trying them to see if either helps you get your libido back. Neither are to be taken consistently. They both need to be cycled off periodically or your body adapts in the wrong direction.