How did you guys get your babies to learn to sit up or crawl? My daughter is 7 months old and everytime we do things to get her to sit up she screams and throws herself backward in a fit, the most she has ever held herself up is maybe 2 seconds.. As far as crawling I know that can take longer but are there tricks or exercises for either experience that can help? My friends son was born on the same day as my daughter and has been sitting up and crawling since 5 months! So hard not to compare and worry about her...