4 month old DD really doesn't like being on her tummy and will cry after a couple of minutes of being placed on it. I dangle a toy or roll a ball whilst making encouraging noises but she squirms and sobs so I end up rolling her back onto her back or picking her up and giving her a cuddle. Consequently she still can't lie on her tummy with her head held up and I worry that she is not going to be strengthening her neck and shoulder muscles and won't enjoy learning to crawl. We are supposed to be focusing on massaging our baby's back at our baby massage class next week and I just know that DD will kick off! Any tips would be amazing and very gratefully received!