Sleep regression?

My 5 month old was the best sleeper, was on a set schedule and once 630-7 hit hed go to sleep and be out until 7am. (He’d wake up around 3 to eat but would go right back to sleep)

Now he’s barley napping at all during the day and is very cranky with only 15-30 minute naps when they use to be an hour & now he literally is fighting his sleep it’s 10pm and he’s still not sleep and this is how it’s been the past 3 days. He’s usually a very easy baby and is never crabby like this. Anyone else experienced this & what can I do to help him get back on his schedule.