Developmental milestones at four month

Which milestones did your LO  reach so far at 4 month old?

My DD  (soon to be 4 month) reached everything except of supporting her weight on elbows. She almost does not use her hands while on tummy. I can't understand what can it be. Neurologist recommended PT but when I asked what exactly is her problem she could not answer. Now I am thinking if it can be normal or if I should expect some long term problems because of it? I feel like I don't get enough information from her doctors, they simply do not have answers, I thought that your experience might be far more helpful than doctor's.