Baby no longer sleep thru the night

My 3m plus baby, turning 4 months in a week time haven't been sleeping thru the night. Its almost 2 weeks. She wakes up at 4 plus in the morning. Am working full time and this is so exhausting. Pls help me! I can't afford to let her stay in cot as my toddler will wake up too since my baby will make noises. #advicepls