Sleep help!

Hi everyone! My husband and I are facing some troubles with our 15mth LO's sleep. Its been 2 weeks and nothing sort of a nightmare. It started out with just fussing around his nap times but he still naps more or less per schedule. Now the LO doesn't want to nap at his scheduled timings (he naps twice a day, 10.30am and 4.30pm), just jumping around in his cot, delaying his nap. Or just screaming his head off until we come get him. At night he falls asleep even before finishing half of his milk, and is an hour earlier than his usual bed time. He wakes up late the next morning too, 1.5hrs past his usual waking time. Does this mean our LO has transisted to one nap? Thanks for reading and any advice in advance!