If you're looking for manga similar to Boku no Omega yo Samenaide, you might like these titles.
Even if we're both beta and even if we're not a fated pair, it'll be fine. Our relationship won't change, ever— Hibiki is a salaryman who has been living together with his high school sweetheart, Koushiro, for 10 years. When they had just met each other, they were convinced that they were a fated pair, but their gender tests revealed that they were both beta. Even though other gay couples can be blessed if they are a "fated pair," it vexes them they can't even hold hands in front of people. They tell themselves that if they love each other, all will be fine, but trivial things make them more anxious each day... But they hear about a misdiagnosis of the gender test one day...!?
Sakura, an office worker at the top of his game working for a major company, has a complex over being an Omega. He hates that Alphas are always oppressing Omegas and has resolved to be Mate-free for life. One day, however, he loses his memory in a freak accident, and finds out that somehow he and his colleague -- an Alpha named Narushige, whom he's always thought of as a rival -- have become mated! At first, Sakura is adamantly against the arrangement, but by and by, Narushige's steadfast compassion, trust, and affection as his partner leave Sakura finding himself attracted to him...
An omega who was pretending to be a beta is suddenly the mate of a top tier alpha!? It happened one night on their way home from a company drinking party. When Mr. Hashida takes care of the drunken Mr. Hayashi, just a small amount of Mr. Hashida's omega pheromones is enough to drive Mr. Hayashi into a frenzy. Despite his resistance, Mr. Hayashi not only has his body taken, but Mr. Hayashi bites his neck indicating that they've become mates. However, it seems Mr. Hayashi remembers nothing from that night... Mr. Hashida considers himself lucky and continues to pretend to be a beta. He decides to hide that he's his mate forever, but Mr. Hayashi (an alpha) keeps desiring his body!
Kaname and Shima have been living together for a year. They have sex almost every day, and things are going well for the couple—at least until Kaname begins to think he’s a sex addict and starts avoiding sex with Shima. Shima, on the other hand, mistakenly believes Kaname is bored of him. Will their long-awaited trip to Tokyo resolve this misunderstanding before it snowballs into an avalanche?
For Saijou Misao, a high school teacher in his thirties, love has become such a distant concept for him that even his students make fun of him for it. One night, while drinking alone at a bar, he runs into Takashi Ryouhei, a teaching materials sales rep that he barely knows. However, he's never seen Takashi look like this before...
University student Kanade Shiiba has had a tight-knit relationship with his overprotective friend Munechika since they were babies. Although they cherish each other dearly, Kanade has resigned himself to the belief that they can never be together romantically because Munechika is an alpha and he is only a beta... or so he thought. He suddenly becomes feverish one day and his body goes into heat, and Munechika is there to take care of him. Now that they both know Kanade is actually an omega, how will their lives change?