How long did it take to feel better once started on antibiotics? Any side effects of the antibiotics?

It's been a rough and sleepless week with LO - maybe a wonder week or a relapse of reflux. Now I have a fever/chills and have had several clogged ducts over the past few days despite being religious about the sunflower lecithin and working them out, so I think mastitis is the most likely culprit. Ugh, I was so looking forward to breastfeeding getting easier once we got past the six week mark... hopefully we'll get there eventually.