If he holds his head ,can  look up when on tummy , holds his hands in middle and puts in mouth, making sounds ,when talked too ,then milestones are normal .

Some times there will be slightly variations in time of development milestones in baby. Need detail history and examination to conclusions. For straining, if child passes normal consistency stool then not to worry. Do burping more.

Detail examination require...so consult in person

You should give more details about your his development, whether he has acquired smiling at you ,weather he is able to hold his neck and head while lifting i  if these two are present you may not worry because rolling over maybe delayed a little bit,, but by this time he must have obtained smiling at you and neck holding second issue regarding the sraining. straining is very common in infants and usually does not have any significance provided he does not have any vomitings ,he does not have bowel disturbance and he does not have distension of the abdomen , that means swelling of the stomach. so if these are absent then s training may be ignored .your only concern should be e about his development. so so you please check again and if he did not attain social smile and neck holding, then you must rush to a pediatrician and get checked thoroughly. thank you

Consultation is required to knw better information and history about the child's overall health. Better to consult Pediatrician.

Dear parents, For details discussion consult me on practo app

1)Has he achieved neck holding? 2) What was birth weight? Was baby full term? What is present weight? Had baby any issue at birth?