4 month sleep regression - any advice?

Hi girls! First time mom here. My son is now 15weeks old and we've been going through what i think is 4 month sleep regression. I need some advice to not go crazy :)

A bit of back story...

I've always put him in bed drowsy but awake. I'd give him his pacifier and his lovey to hold, and he would stare off into the air or the side of the crib a whole and fall asleep. With naps that was basically the routine, we didn't need anything more complicated. And i put him into the crib when he was up for an hour and 15min and he would fall asleep before hour and a half or hour and 45min tops. Always the same, never any problems.

Then in the evening the routine was bathing him, feeding him after bath, singing a certain lullabye and rocking him a bit until he got drowsy. Then my husband swaddled him and we put him in bed. White noise or calm lullabye music was turned on (Sheep Liz toy). He got a pacifier and we put his lovey close to his head. And he would doze off.

So I thought i taught him self soothing already, which according to my internet research, is reason number one for problems when 4 month sleep regression starts.

So what's happening now is that he doesn't ever get drowsy. :D

I still put him down for his nap after an hour and 15 min or an hour and a half of wakefullness, when he starts getting a bit cranky. But he is wide awake, his eyes wide open. He spits his pacifier out a hundred times and mostly starts screaming his lungs off after being in the crib awake for more than half an hour. Sometimes he starts screaming sooner than that.

He is also physically fighting sleep... His eyes will be almost closed, he has calmed down, looks like he's about to doze off... And BAM! He starts kicking like hell, moving his whole body and grabbing his pacifier and pulling it out and he wakes himself up completely and of course, he starts screaming sooner or later.

The evening isn't any better. The longer routine does not help, he again does not get drowsy at any point, just crankier by the minute until he starts screaming.

I'm honestly at wits' end.

Also, he is EBF and i'm absolutely sure he is not hungry as i have an overabundance of milk and he will not take the breast when offered.

Also, at almost 4 months old I doubt he is overstimulated given that i always try to put him to sleep before an hour and a half of wakefullness. He also can't be too tired as we're still (somehow) managing 12-14h of sleep per day.

Any advice?

A pic of his big butt for attention grab :)