@RPG Hacker, have you invested in an ergonomic chair or gone to a physical therapist (assuming you can?) Do you also know what kind of pain you are experiencing, like, is it "pins and needles and do you occasionally feel numbness in a part of your body (implying nerves)" or is it "achy" or "tender" pain (meaning muscles?) I think you really should go to the doctor, and your doctor will probably refer you to a physical therapist who will have you do a set of exercises targeting your painful muscles. You can also try looking up what kind of stretching and gentle exercise is good for those muscles. It
is intensive starting out, but as long as you maintain it, you can keep your pain mostly tolerable. Also, keep as hydrated as possible and keep your potassium levels sufficient (coconut water, banana, potato are all good sources) to reduce muscle spasm.
There's also the possibility of trigger point injections if you have particular spots which are super sharp excruciating pain to any pressure application- it involves a little cortisone which is a steroid, and a local anesthetic to numb the pain a bit. You should let the muscle rest for a couple days, then use it regularly to keep benefits. In no way do you want to rely on steroidal treatment because you can only have it done so many times in a spot before it will actually destroy the tissue. They definitely help, some spots better than others. Didn't do much for my neck and shoulders in my case because those areas suffer from stiffness and inflexibility, but it did wonders for the back and hips I had crippling pain with, making it manageable now with just hydration and a bit of stretching whereas before I could barely drive and needed new insoles every 2 weeks to support them. I do end up drinking 3/4 to 1 full gallon of water daily so I don't wake up in pain though.
For your back, get an X-ray done. See if you have a degenerating disc causing pain to radiate through your back. (You mention investing in a foot rest, so I am wondering if it's specifically your lower back you're experiencing pain with, as that would cause problems all the way down your legs too.) If you're experiencing tailbone pain, a donut cushion has worked wonders for me when I lacked a soft-enough chair otherwise. I also used a lumbar support pillow for driving until I built enough stability in my back and legs to do without on most days - I strongly recommend that if you can affix it to your chair without it wobbling.
If you are a side sleeper too, you don't wanna do that - that increases the likelihood you're straining your shoulder or neck by sleeping on them funny. It'll make them more stiff and more achy. Are you OK sleeping on your back? That's the ideal position, and it may work better for you if you put a pillow under your knees to make the position feel more natural.
Regardless of whether you do go to a doctor soon, make sure you give yourself a break every two hours to stretch and walk around, or your muscles will start to lock up and feel crappy. And keep water with you! Lots! Office work is just as bad on your body than heavy manual labor. D=
@lion, you are talented. Coding is not a destination but a journey. I hope you won't be too down if you don't get the result you are hoping for right away. Coffee is also a great reward for yourself. It even goes hand-in-hand with coding! You have the right idea too: if there is a fee, but you're making more than what they're charging and you don't have money coming in anyways, it's worth it!
I miss taking long walks around town with sights set on a coffee shop a mile away rather than the end of the street, just for the goal-driven exercise. I should get back into that routine. I want a small, frothy espresso drink.
Just look above you...
If it's something that can be stopped, then just try to stop it!