Use the gym. Do it twice a week at least. Learn how to use the gym. Get a trainer for a while so you learn. Get a good chiropractor who can guide you as to what parts of your body need the most work.
Solid advice, apart from the chiropractor. By all means engage a physiotherapist / physical therapist, but not a chiropractor. In my experience it's all spine spine spine with those people.
So you have a sample size of one and you are using that as the basis for your advice to a group of people who are not you? Not to rag on you, but this is a common problem with health advice. As soon as we move away from studies people have a thing that works for them that they swear by. We need actual studies and science before we decide one thing is better than something else. Anecdotal evidence is pretty worthless - not totally worthless cause when you are struggling you'll try anything, but pretty worthless.
But just for fun, to balance your one chiropractor I'll give you a different chiropractor story. I hurt my back playing rugby when I was younger, my mum had a chiropractor who she swore by and brought me to. After about 8 weeks of treatment with no improvement I insisted we go to a real doctor. Turned out I'd broken bones in my back. The chiropractor was just treating me for a slipped disk "because 90% of people who come in have them".
I was in a torso cast for 3 months. Needless to say I'm not a huge fan of chiropractors.
You had a bad chiropractor, who probably would have made a bad doctor as well by the sounds of it (just assuming a rugby injury is a slipped disk? did he even check? was he even able to check?)
You'll find tons of stories of malpractice by all sorts of doctors. (I wouldn't go to a chiropractor if there was a chance that x-rays might be necessary for diagnostics.)
A chiropractor isn't a doctor though, does malpractice even apply to them? It's just quackery from start to finish isn't it? That'd be like suing your palm reader for fraud because they made some prediction that turned out wrong.
Chiropractice is not quackery from start to finish. A chiropractor solved my rsi with simple adjustments and some home stretching and joint exercises. A chiropractor fixed my mom's debilitating back pain after pregnancy. But there are many quacks in the field because it is unregulated, and many practitioners also hold metaphysical or folk beliefs that are totally unscientific at best. I have stories about those too. But a good chiropractor will simply diagnose the level of adjustment needed and provide it, and show you how your muscles and skeletal structure are causing you pain.