You would definitely know if the milk was bad when you smelled it. You would have tasted it too. I accidently gave my daughter bad milk (wasn't due to expire for another few days) and she took one sip and said ew mama....I dumped it immediately and she was fine. The lactose free milk def has some properties not like regular milk so it very well could've not handled being warmed up. Like I said, if it was bad, you would have noticed when you smelled it. Hang in there ok!