L.S.
I went through a similar situation when my daughter was 9 months old. She got rotavirus (even after being vaccinated for it) and lost her appetite. I was able to still breastfeed, but she wouldn't take anything else. It took her awhile to bounce back, but she did eventually. Especially because your son was sick for so long, it may take some time to regain his appetite. Give him whatever he will take, if he wants to breastfeed, do it, if he wants to eat crackers and peas, let him. If you are concerned about his weight loss you should take him in to be seen, but if they tell you, like my pedi told me, to replace breastfeeding with pedialite, DON'T! Breastmilk is better than anything you can find in the store (your doctor probably won't say this, but I was shocked when mine did, so just an in-case warning). Good luck and just give him a little extra spoiling over the next week or so.