Refusing

My 4 month old is refusing to nurse. She just screamed and kept pushing away. I'm at church so I couldnt do anything but give formula. What's happening??? Does she not want me anymore???? What do I do? This has been going on a week or 2 but today she just flat out refused. She is drinking the bottle so I know she was hungry though. Plus I tried to get her to nurse about 10min with screaming and pushing my breast away

Update......

My cycle started back today. My baby is 4 months old. Can this be why she has been acting strange????? She has nursed today though?? What should I do