Girls, my daughter is almost three months old. Lately she doesn't want…

Girls, my daughter is almost three months old. Lately she doesn't want to sit in a baby swing or on my hands. I lay her on a mat. She tries to turn over onto her stomach immediately. I help her turn over onto her stomach - she crawls somewhere and coughs. Back to her back - again she gets strained and tries to turn over. Trying to get out of the swing. What kind of thing don't I understand?