Is that a spider bite or do we need to operate?

Not exactly sure what happened, but I remember getting an itch on the back of my leg on Tuesday night. I was sitting on the couch. The next morning, I woke up to a big old red swollen mark on my leg. Throughout the day, it got bigger and started to feel really sore. It was also hot to the touch. So I wasn't sure if it was a spider bite or what but whatever it was it was infected. So I marked it on Wednesday night with a pen to see if it was growing. the next morning, it had gotten bigger by one inch outside the pen mark. So i knew i had to go to the doctor. Also, it was huge. the red swollen part is the size of the palm of my hand. and it hurts to walk sit or stand. when I'm laying down it hurts still but not as bad as the others and if you touch it or bump it, i wince and say "mamasita!" because it hurts so much. So i went to the urgent care last night after speaking with a retired doctor from the ward (the son of some one in our ward) he said that i needed to get to the doctor right away because of how fast it was swelling/spreading. so i went to the doctor yesterday and he checked me out. he said he wouldn't know exactly what it was unless he did a biopsy (like a staph infection) but he did ask if i got bitten by a spider. i said i wasn't sure because i didn't notice a bite, just an itch so it was possible. so he marked it with a pen (again) and gave me a super shot of antibiotics. he said that if it got worse by twenty four hours to go to the ER. So far, it's not any better, but it's not any worse. He also gave me a super antibiotic to take twice a day. and a topical cream. it sucks. i have to do warm compresses as well and keep my leg elevated to keep it from spreading and getting more swollen (kind of hard to do with two little ones but whatever. I'm just relying on moma to entertain herself today). It seriously hurts so much. it's weird. i limp when i walk and now my butt hurts because of the antibiotic shot.
I was talking with my BFF "v" on the way to the doctor yesterday and she was just like "you always have the weirdest things happen to you!!" and i was like "I know. it sucks!!" but then we both divinely decided that it was because #1- I can handle it because I'm a tough chick or #2- because i learn from them and then share all my weird stories with every one because i have a big mouth and then they can learn from them and be more aware when anything weird happens with their own bodies and get it taken care of.
I also talked with my dad last night and I totally inherited this from him. My mom never has anything weird happen to her body and never gets sick. but my dad, he is always having some weird reaction or allergy or something totally bizarre happen to him and I'm the same way. couldn't i have inherited something else from dear old dad? like his love of exercise and healthy eating. yeah, that one would have been nice. but NOOOOOO!!!! i get the weird freakish medical things happen to me. I'll go to the doctor and the doctor will say "you're allergic to THAT?? that's a very rare allergy!" "or... I've never seen anyone with THAT before" oh. that's comforting! like when i had my hernia with thumper. all the doctors said "I've never seen a hernia in a pregnant women in THAT spot before!" or like the fact that I'm allergic to ibuprofen and break out in crazy hives all over my body if i take it. just weird random things. how annoying. so anyways. back to the THING on the back of my leg and i say THING because the doctor has no idea what it is and just guessed. he said that if it gets worse today that I have to go to the ER because it could be a strep infection which i guess is pretty serious. at least he made it sound that way and did a good job at freaking me out. so hopefully this medicine will do it's job and get rid of the infection. I really have grown fond of my leg. it would be a shame to lose it. ha!