I feel like the reason his reaction was so much worse was because he had to suppress his sexual desires to a point that the medicine wasn't working anymore. In other mangas omegas that can't use the medicine usually have someone they have sex with while in heat but in this manga he's faithful and his fated partner is too young so physically and mentally he has to battle his desires so it quadruples in effect.
I mean his reaction from the first time he met Haruka. From the ones I'veread, they mostly just 'know'. But Chika was going mad the first time he met Haruka. Can't say I like it though. He looks like he's suffering so much now :(
I feel like this is an overreaction of romega. In other manga it's not as bad as Chika's reaction. But I guess this is the mangaka's version. I wish he wasnt suffering so much