Suggest Treatment For Cellulitis And Fever

Hello, I have a two year old daughter who got bit by something (suspecting a spider) last weekend and it started swelling and pussing so we took her to the ER. They treated her for cellulitus by giving an antibiotic. I had to give her 2 mL every 6 hours until the bottle was gone. However, with her and an infant, I sometimes got caught up and started forgetting. After about 4 days I stopped giving it to her in fear I was doing more harm than good by skipping severeal hours before giving her another dose. That was about 2 days ago and this morning (it is now 1:26AM so around 11AM yesterday) I noticed a fever after a nap. It was 103.2 and I have been monitoring it, it hasn t gotten any higher than that. I gave her tylenol once and it helped a bit, but it started to go away and then came back after yet another nap and is only seeming to get high while she is laying down to sleep. I was just monitoring her heart rate when I noticed she was breathing a bit faster than usual. She is at 150 bpm and 37 breaths. Could this be from the bite a week ago because I didn t finish her antibiotics? Should I start them again? They are still in my fridge.