12 week old has croup

12 week old had all symptoms of croup so we took her to doc this morning and she was given a single dose of steroids and Tylenol and we were sent on our way. 
Now after reading more about croup I see the doc should have checked her blood oxygen levels (I'm a FTM and have no idea what to request at the doc) all he did was listen to her chest for 2 sec and was gone. 
It's been 12 hours and she's worse, screaming, drooling excessively (not teething), Tylenol isn't helping, cough is worse, sleeping waaayyy more than usual, almost a labored snoring sound from chest while she sleeps on back
QUESTION: 
Should we take her to ER to be re-evaluated since she's so young and is getting worse?