Beta is suddenly pregnant, turns out is omega after being with an Alpha he always looks after and sleeping with Alpha during a rut Alpha is younger and grew up following the Beta and Beta promised to marry Alpha if they both were alpha and omega when the Alpha was a child Beta is always around alpha during his rut and thought to have changed because of that. Alpha is smaller and kinda cute/pretty looking while Beta is more larger

This sounds so familiar. Not sure this it but maybe Love Shuttle

thank you for the help! sadly it is not the one

Is it The Alpha's Bride? That's the first name I think of when reading your post. @ Block Blast Do you think so?

check this list https://www.mangaupdates.com/series?category=Beta%20Becomes%20Omega&perpage=50&exclude_genre=Shoujo_Shounen_Seinen_Josei_Shoujo%20Ai_Yuri

it includes everything BL marked "beta becomes omega" there are only 48 results

Quote from hollyjohnson

Is it The Alpha's Bride? That's the first name I think of when reading your post. @ Block Blast Do you think so?

Thank you but that isn't the one but definitely something new to read

Quote from lollylopmr

check this list https://www.mangaupdates.com/series?category=Beta%20Becomes%20Omega&perpage=50&exclude_genre=Shoujo_Shounen_Seinen_Josei_Shoujo%20Ai_Yuri

it includes everything BL marked "beta becomes omega" there are only 48 results

Thank you so very much for the list! found it on there!

https://www.mangaupdates.com/series/f75yzqn/pheromone-baby