Hi M.! I know it is concerning but honestly this sounds like very normal nursing behavior. Continue offering him foods at meal times and he will eventually get it. Also, if the medication is interfering with his food intake, it is a good thing that you ARE still breastfeeding because you can be reassured that he is getting a nutritious healthy snack from your milk. My son went through periods like that and sometimes when he's not feeling well or wants to be close to mom he nurses quite a lot without eating as much solid food. (My son will be 2 in a few weeks). As long as he's happy and healthy, just be persistant and continue to offer a wide variety of foods.
Also, La Leche League may have wonderful tips for you... I know they've helped me out a lot!!! Here's the website... http://www.llli.org/
You can even find a group close to you and contact a Leader personally.
Enjoying breastfeeding,
K.