Baby motor skills & mental health.

I am very concerned about my baby's development. Baby is 4 months old but he doesn't reach for objects &not even tries, mostly doesn't seem to be interested in them. Also he seems to have head lag as when we try to pull him up by grabbing his hands his head stays behind. Our pediatrician has advised us some occupational therapy and exercises but I am still worried about him as some people told me that baby should reach for things now , should laugh often and also look at the direction of sounds. He also doesn't roll over by himself & can't control his head. He also had an EEG test which shows abnormal epileptiform discharges from right side of brain . After birth he was about 1 month in nicu where he also had some seizures 3-4 times , blood platelets were low. I read somewhere that it can be sign of autism which scares me a lot. Please suggest me what can I do now , should I be worried about his mental & physicla health. Also please tell me how to identify for seizures.