8 oz. of water every hour, yes every hour. Watch the clock and when the big hand hits 12, drink a glass of water. At night, keep a bottle or two of water by your bed so you can drink if you wake up as well. You will have to use the restroom a lot but it worked for me when I was pregnant so I continue 'til this day. I'd rather use the restroom more than have a prolonged cough.
When you have more energy (in the morning?) get a lot of crafty ideas together bags or shoe boxes. Then throughout the day, you can get out one bag or box at a time. Teach him to clean up and put everything back in the bag/box and then he can have another bag or box. I'm sure he is a busy boy at his age. You can get lots of ideas online for homemade playdough, homemade soft pretzels, etc. would make long ropes of the pretzel dough and then let my kids make their own shapes. They loved spelling out their name and then eating them. I used margarita salt for some and cinnamon sugar for others... Find things you can do sitting down.
Rinse the dishes but don't wash them if you are exhausted. Just ask your husband if he could do those for you. Let him know ahead of time what you will be doing with your son and you will need his help with the dishes.