I don't think taking four days is necessarily a problem, unless you're putting several drawings in each episode. Not everyone uses a style that allows you to make a whole page in a couple of hours. Practice will make you more efficient and result in less mistakes that require you to redraw stuff, but some things are just going to take a long time regardless of your skill level.
If your work is an illustrated novel and you're feeling pressured to add pictures because this is a comic hosting space, have you considered putting it on AO3 or other fiction sites that allow images as well as text? Most illustrated novels don't have lots of images per chapter/episode, so you don't really need to be drawing several, especially if they're high detail and take a long time.
As for the wrist injury, there's nothing wrong with taking a break to let it get better. Readers will understand, and they'd rather have you stop posting for a bit to recover than do any permanent harm. If that's not helping, look into wrist splints to wear at night. I started using them for RSI because I took a break and just didn't get any better, and it was almost completely cleared up within a few weeks.