New relationship,kids

So I’m in a new relationship (2 months) we both have kids from a previous relationship that are still dealing with us being in another relationship. I have been on birth control religiously with the exception of one night but took it asap and continued to take it on time afterwards. My period is late and I’ve taken 2 tests both negative but my SO is freaking out cause he doesn’t want his other children to hate him if i end up pregnant. He said he would want me to get an abortion but I don’t know if I could do that. I’m just a little worried at this point and looking for anyone that has been in a similar situation with some advice. Tia.