12 week old won’t nap...

He was a great napper and it seems like every week he naps less and less per day. He’s down to two hours the last couple days which is a nightmare because he’s tired but won’t nap independently. I’m fine with a nap or two on me but he won’t nap at all in his crib even tho he sleeps fine in there at night. I’ve tried anything and everything I can think of and it’s just not working.

Has anyone else gone through around this age?? Im losing my mind and he isn’t small so carrying him around all day is killing my back. Everyone keeps saying it’s a phase and it’ll get better but when? How? What do I do?? Feeling so discouraged