Hooked50s

I'll be turning 52 this month. I've been watching porn since I was about 13. It began with magazines, moving on to internet (static) porn in the 90s and high-speed internet (video) porn for the last decade or so.
I married in 1996 and the marriage lasted a few years until we divorced in 2000 for reasons directly attributable to my porn habit. We had no kids (thank God!). I remarried in 2003 and have two kids - a son aged 17 and a daughter aged 13. This marriage too is on the rocks, again for reasons directly attributable to my porn habit, and I currently live separate from my family.
Living alone, I watch porn and masturbate multiple times almost every day, and binge (about 3-5 hours non-stop) probably thrice a week on average.
As a direct result of my porn habit, I've been unfaithful to my wife several times. I don't know if it makes any difference, but at least I've never loved anyone but her.
Aside from this, I'm socially well-adjusted, I've a stable job, I'm a keen musician, and I have a number of hobbies and talents that I have mostly no time left for after porn, and so have allowed to waste away. Only my music really remains.
I have tried multiple times (I've lost count) to quit and failed every time. The longest I've been continuously clean for is about 45 days, and I've found that the longer the abstinence, the worse the relapse.
I suffer from lack of sleep (due to staying up late for porn), poor concentration, inexplicable memory lapses, 'switching off' occasionally in social gatherings, and frequent bouts of low self-esteem.
I've carried a huge burden of guilt and shame due to my habit, and fear that I'm a bad husband, bad father, and a shitty example for anyone.
I desperately want to be free of this burden, and my guilt over the pain that I'm causing to my loved ones.