Help Please!!!!

My 4 month old will not take my breast. I am exclusively breastfeeding but I'm always on the go. I work and I have 3 other children, so I pump a lot. However at night I would nurse. So twice each night she will get the breast. The last 24 hours she has not been on the breast because she refuses to latch on. She can be hungry, rested, calm, etc but she wont latch on. She acts as if it's a foreign objectS help!!!! Please!!!! Any recommendations???