Probably this one?
https://www.mangago.zone/read-manga/it_s_my_baby/
I saw that someone probably already gave the correct title but I got a rec that's not ABO
https://www.mangago.zone/read-manga/wedding_plans_for_mr_mr/
Absolutely this one.
It’s not that one, but thank you. I’ll definitely read this one.
It’s not this one either. But wow, thank you. I didn’t know about this one yet.
Wow, this is the one! Thank you so much. I spent so much time looking for it and couldn’t find it.
Yes, this is the one! I finally found it with all of your help. Thank you so much.
I'm glad I could help ^^
I'm glad °°
There’s a manga, which is Omegaverse, where the Omega works at an arranged marriage company. In this company, he meets an Alpha he once had something with. From there, he starts the struggle to find a match for the Alpha while trying to hide the child he had with him.