I wouldnt worry at all! I was beginning to worry about callie to, not rolling over, not grabbing toys.. ect! it seemed like it happened over night.. she is just over 5 months now, at 3 months she was batting at things.. 4 monts old she would hold on to things.. a few days after that she was grabbing at them.. Now when she is in her bumbo sitting on the floor if she drops it she will bend over slightly to get it!.. Just remember, once they start, they wont stop!!! someone told me that about when I was getting worried about her rolling over I said I DONT CARE!!! I just want her to start.. and since she has.. she hasnt stopped.. LOL..