I definately think that you have a bigger problem that feeding at the moment, cycling your tank!
If you want your fish to make it, you'll need to get yourself a test kit for ammonia and nitrite, as a bare minimum. I would recommend the API Master Test kit for Freshwater. It'll run from $15 to $30 in some places.
I would also look into products that remove/de-toxify ammonia to give your fish a fighting chance. Ammo-Chips comes to mind.
You're in a much dire dituation that you may think, read up more about "new tank syndrome". Hopefully, you can still have time to save your fish.