My 3 mo old fights sleep. He is visibly exhausted, but will twist and cry and fight it until he just falls asleep. Is he ok? What can we do?

Close to heart. Babies love the rhythm of mom's heartbeat - since they listened to this inside mom's belly - if you are busy to relax just carry baby in the baby carrier close to your heart. Eventually you can create consistent rhythm and relaxation routine for the baby. Children love consistency.
Lots of possibles. At 3mo an infant does not understand the concept of sleep as a solution to tiredness, they often think u are their solution to everything and fight to stay awake so u can fix things. That said, baby should be able to drift off to sleep at least some of the time unless somthing is bothering them. I would try a warm bath to relax baby, then put down awake and sooth from a distance.If no help see dr.
Testing you ? If he falls asleep on his own and wakes up acting fine and has no other symptoms i would think he is ok.Just make sure he has comfortable clothing, ensure proper room temperature and also make sure he does not have a wet or dirty diaper.