Ex got girl pregnant

I just recently found out that my ex and baby daddy got his new girlfriend of a few months pregnant. (She's 15 he's 18 I'm 17 turning 18 in two months) It bothers me so much because he has absolutely nothing to do with our baby nor does he help with our son in any way (my sons 2nd birthday is in 2 weeks and he won't even talk to us now because of the new baby) What bothers me so much is he does nothing for our baby and then goes out and has another kid he more than likely won't take care of because he likes running from his problems. Okay now to her. She literally is copying everything that I did during my pregnancy and do now. She did the exact same baby shower theme I did with the exact same meaningful things I did at mine. She's using the same OB I did, she plans on taking her son to the same pediatrician I did, literally just everything. (It shouldn't bother me but it does) Also one of the girls that threw the baby shower for her. Messages me and asked me to stay civil with the girl because "she's having a really hard time with this right now and our baby daddy isn't helping her." Okay and? I've been having a hard time raising his first kid by myself for TWO years, so many people even tried telling her when they got together what would end up happening and she didn't listen! I do plan on staying civil but she acts like I'm supposed to throw a pity party for her or something because he's not helping with anything which she should've known because the whole 9 months they've been together he has seen our baby like 5 times and hasn't help with him financially in any way at all!