How long does rash last?

I found a bullseye rash on my abdomen about a week. I went to the doctor and got 3 weeks of doxyclicline. I've had 3 days so far and the rash is growing and growing...How long does it take once you start antibiotics to see the rash get smaller? Mine is growing an inch in diameter every day.

How is the rash now, RN513? Better, I hope.