Naps and awake time

Hey usually my LO will be awake for about 2 hours then go for a nap. But lately he’s been up for 3 hour wake times but gets cranky half way through cause he’s getting a bit tired but won’t soothe himself and will scream in his exerciser or anywhere until I hold him. But won’t fall asleep till the 3 hour mark. How do I get him to not be so sleepy Halfway thorough his wake time or get him to self sooth? He will be 5 months on the 11th so any advise would help. TIA