You told your husband about this other man after you'd developed a strong connection with the other man? Your husband wanted separation? Is he aware you've started sleeping with the other man? Just to clarify.
It sounds like all three parties are not actually in communication. It sounds like you're doing a lot of talking with each of them. Does your husband feel any desire to talk with this other man or does he regard him as your affair partner?
It is not wise to rush into an abortion on the basis that babies can be messy and exhausting or fears of being 'unable' to handle things. The emotions that often come in the wake of abortion often last much longer than pregnancy, and this is still a child's life we're talking about. There are plenty of resources out there.
Have you confirmed you're pregnant yet?