Burning sensation is a typical presentation for irritated nerves. After surgery, as your nerve endings heal they may be irritated. Burning sensation, pins and needles, electric shocks, itchiness that you just cant's scratch are all normal in the initial healing period and represent your healing nerves randomly firing as they heal. When this is either too uncomfortable or if it not going away your surgeon can prescribe you medications for nerve irritation to help you.
your temp of 37.5 can be due to anything, including inflammation in the area of your breast healing. It does not sound like an infection. If you are still concerned, see your plastic surgeon so that he/she can examine you directly.