Mc is afraid of losing the baby if he tells fl, and being a male omega, he has little chance of getting pregnant. I think he has enough reasons to keep it a secret.
What real reason does he have to think he'll lose the baby if he tells the father??
Even if the father doesn't want the baby, he can still run off and raise the baby on his own. But not telling the father is absurd.
Sorry but have you not paid attention to the story? ML hates omegas who try to baby trap him, and mc fears that if he finds out about the pregnancy he will force him to abort. Remember that ml treats mc coldly, they're not friends. Their relationship is purely sexual without feelings on ml part, plus ml mother hates mc and tries to settle her son with other people. All of these things affect his decision not to tell the father. Check chapter 11.
I hate when they don't tell the father they're pregnant