Will only nap when held!

Help please my 5 month old will only nap in my arms, no one else's. He'll go down fine at night and can even self soothe. But in the day time it's a different story I can rock him to sleep till he's sound asleep and as soon as he's anywhere near the cot he's wide awake. I've tried putting him down when drowsy, tried putting him down when awake and going in when he starts crying and soothing him etc but nothing works! He's got him self on a good nap schedule and can nap for 2-2.25hrs a time but it's means I never have any time for anything! I've been trying for 3 month's to get him to nap on his own. We couldn't in the beginning as he had pretty bad reflux but as we got his medicine sorted he started sleeping in the night and we thought day naps would follow but no luck. Any advice would help please!