You poor thing. The self-isolation creates panicky thoughts, and you mustn't feel guilty about anything -- none of this is your fault!! I would also agree that if your son is distressed it would be reasonable not to isolate from him. As for you, my practical advice (having recovered at home a few weeks ago) is as follows:
Unless you really can't manage, or fever is very high, then try not to take paracetamol. The fever is good. The virus dies at high temperatures and the fever is the mechanism for getting rid of it.
Take guaifenesin (basic cough medicine) to thin out the secretions. The mucus is so thick you don't SEE it (not like a cold at all) but I felt plugged up for weeks. Also saline nasal spray, hot steamy air (eg stand in bathroom with shower on, as you would for a child with croup). Watch videos on how to cough (JK Rowling posted one) if the cough starts, which it may not.
Consider buying an oximeter to measure your oxygen saturation, that way you can call 111 at first hint of level going down. I didn't do this because it wasn't recommended by anyone in late March. Realistically this is probably overkill anyway unless you have a pre-existing condition. As a young healthy person you have nothing much to fear.
Take zinc and vitamin C supplements.
It's a very up and down illness. The down was never as bad for me as with pneumonia or flu. I didn't call the GP or 111 and never felt in any real danger. But I did start to wonder if I was ever going to recover! After three weeks I started to get a lot better. Now feel completely healthy.
I think it's normal to get pain in lower ribs and back, and for me it felt a bit as if I had acid reflux. This passed after a couple of days and wasn't a severe pain, I just found it a bit frightening.
Consider taking a baby aspirin every day. Lots of evidence to suggest that covid-19 is at least partially a clotting disorder. This made me feel as if I was protecting myself, anyway, and is pretty harmless.
The single most helpful thing for me was very hot baths. I found lying in a hot bath for an hour twice a day very helpful. Otherwise just try to rest, watch TV/ play games on your phone etc, don't expect much of yourself, and drink LOADS of fluids and it too will pass.
Once it does, there is some comfort I think in knowing that you're almost certainly immune for the time being and no longer a potential threat to every elderly person you pass on the street. Even if you're not immune, once you've recovered once there's no reason why you wouldn't a second time.