WHY, have you not gone to the doctor already??
Obviously what ever it is, it is very serious.
There is one spider and it's bite that is very, very serious, like Big time serious. It is the 'recluse' spider. I don't know if you have them in your area of the country - I think they are throughout the US, but more so in some parts.
You need to look it up on the internet and look at the pictures of its bite, symptoms, etc. ...the pictures are Not pretty!! What you describe sounds like it 'could' be.
But do a little research, then get your B_tt to the doctor Today! Even if it isn't this, whatever it is needs to be looked at today.
Wish you the best!