Hi, welcome to BW
When things aren't working, sometimes its about when you're expecting LO to go to sleep rather than that he's just lost the ability to sleep. Their sleep needs change so fast at this age that its more likely he needs a routine change than anything much else. Having said that, if you've been feeding him to sleep and he's waking looking for feeds frequently, that can be a time that if the routine is right, some form of assistance in settling to sleep (other than feeding) is required.
What are you aiming for with his routine?
Have you ever tried the EAS order of things, so feeding when he wakes from sleep, then play, then sleep (without a feed)? You can settle to sleep with shush/pat or some variation - I would recommend starting with that rather than going straight for PUPD as its a method of last resort for when shush/pat has been used consistently and appropriately for 2 weeks with NO improvement.
At 5 months, a typical routine would look a bit like this:
7 - wake, feed
9:30 - nap
11 - wake, feed
1:30 - nap
3 - wake, feed
5 - 45min catnap
5:45 - wake, feed
7:45/8pm - asleep for the night