Poor Bradley and poor you!
It sounds like all of the disruption (hospital, immunizations etc) has maybe got him off track a bit. If his sleep has been disrupted for a significant amount of time it is likely that he is overtired which just ends up in a viscious circle
Ciara was in hospital for a week when she was 2, and it disrupted our routine a bit when we came home. The things we focused on were;
Giving her lots of love and attention - making sure that she was confident in her surroundings and happy in her bed. It might help to introduce some play time in the bedroom/on the bed for Bradley to help him feel safe and secure there again.
Find a consistent approach and stick to it. So if you want him to sleep in his bed then perserve with this, no matter how difficult!
Wind-down time/bedtime. If he is overtired it might help to have an early winddown time/bedtime? Does he know when nap time and bed time are coming? Making these really obvious may help with structure and with his comfort in what will be happening.
OOPS ... just seen the time, going to be late for nursery pick up ... check in later