How to stay strong Ina custody battle

My kids father is threatening to fight me for custody because I put him on child support and he's saying that he's not going to pay for a kid he doesn't see yet never wants to pick him up when I offer. I have messages of him threatening me and more stuff but I just can't get this anxious feeling out of me . Like I just want it to be over already I have taken care of our kid since the day he's been born alone. And to just have to give him up to a stranger sickens me to the core. I feel so exhausted how do you get through this for those who have experienced something similar