Holy shit I thought this was completed already!

Look at this through Omegaverse rules rather than real-world rules. Su-ah is an Alpha. Juhyeok is an Omega. One who was convinced, before his manifestation, that HE'D be the Alpha, and Su-ah the Omega. So you have that "betrayal" from the beginning. Then there's his judo dreams--which are already against him, simply because he's an Omega. Then you have Su-ah's (seriously wrong) scenting of him for years, making him dependent upon his pheromones.

Juhyeok is an Omega. He doesn't want to be, tries to live like he's not, but he is an Omega. This will always be true. Nothing can change that. Quite frankly, he needs to come to terms with this, and not blame it on Su-ah--which as we've seen, he kinda DOES. It doesn't make any sense, but he does. By the same token, Su-ah CANNOT understand his feelings on it, because he'll never be an Omega, he'll never have to deal with Omega heats, Omega pregnancy, Omega hormones, none of it. Add in Juhyeok's insane amounts of stupid pride, and, well... 

Su-ah is an Alpha. Juhyeok treats him as an idiot, a child, and someone incapable of doing anything but crying and clinging to him, but he is an Alpha. This will come with instincts, drives, and urges that Juhyeok simply CANNOT understand, because he'll never experience them. He brushes off Su-ah's jealousy, not understanding an Alpha seeing "his" Omega coveted by another Alpha.

These two need to sit down and talk. Without Juhyeok's pride and temper or Su-ah's emotional blackmail getting in the way. An open, honest conversation. Which they've never had.