Baby no longer sleeping through the night

Hi everyone

My 4.5 month old just started sleeping through the night when she hit 4 months. She would have her last bottle around 8 or 9 at night and sleep all the way until 7am. This whole week she has not been sleeping like that. She will have her last bottle at 8 or 9 but now she wakes up almost every hour crying. I get up to give her pacifier and she sleeps but then she wakes again every hour like clockwork. I don't get it what changed? Please help I'm exhausted.