How to get the baby to nap, please?

I have a baby boy who is 4 1/2 months old. I've been breast feeding him and am hoping to continue it for 1 year. He had been sleeping through the night for 5 hours, but he refuses to nap during day time. So, it's hard to schedule him (we'd tried to schedule him, but it didn't work) We've been trying to put him to bed whenever we see him yawn or look tired, but he refused to nap. I checked everything, he's well fed, had dry diaper. Some said that's because he doesn't know how to relax himself to sleep, so we sang to him, walked him around, rocked him, we wrapped him, shh him, did all the 5 Ss but he still ended up with historical crying before napping. I feel so bad for him. His napping and sleeping each day is about 10 hours total, I heard that the baby needs more than this for their brain developing. Is there any suggestion, please?