Spider bite!!! what should we do?


So my husband got bit by an unknown spider within the last 3-4 days. Saturday night we got back from the zoo and noticed he had a kinda big red spot but it wasnt anything we worried about. Sunday we woke up and it was twice the size, very hot, and very minimal pain when touched. This morning he went to the doctor just to make sure it wasnt anything to worry about because it was growing. This is what it looked like this morning.

He was told to take an antibiotic and tylenol and if it grows to come back on Friday, she was sort of rushing him out. Now, it is so much more feverish and its extremely painful for him to walk. He also was walking into the bathroom and his pupils got insanely huge and he stumbled backwards and said he was light headed. I dont know what to do. He works on his feet but he cant keep taking days off. Should we go to the ER? Or do you think he should give it some time? I feel so bad for him!