Help pls

So my bf recently told me he found out about a child he never knew he had she kept the child a secret for 10 months now she cmes back an says she’s tired of being a single mother . My heart hurts my head hurts I love him so much and to here that he has a baby with someone else kills me . I kinda feel selfish for thinking lik this but I wish that was my baby I should be having g his first child like he keeps saying I’m going to leave him and I don’t want to I love him so much and having a child that you didn’t know about doesn’t change that ... I just idk how I feel I told him one day at a time thatsliterally all I can do .. writing this rn I’m tryin so hard not to cry