CHILDRENS LAST NAME?

long story short,

Me and my partner (of 3 years on and off) fell pregnant when we had only been together for 6 months, unfortunately our little boy was still born, I grieved on my own, I planned our sons funeral on my own, I upkeep his grave on my own. No input/effort made from my partner or his family at all. 12 weeks later I fell pregnant with my little girl, again he didn't buy her much, didn't come to many appointments/scans and just generally didn't seem bothered, had my girl by emergency section and when she's less then 3 hours old hes gone home for a sleep/shower and too see his friends (no problem with that but come on I've had a section, can't really move & needed help!)

He's pretty much a part time dad, as and when it suits him, I found out he was smoking cannabis instead of spending time with our daughter & although I knew he had smoked it when we first got together, he promised he'd stop for the children. (BIIIIIGGGG LIE) i kicked him out and he went back to his mums.

In October 17 I found out I was 10 weeks pregnant with #3!! He's not done a thing, asked me 'when are you getting rid of IT then?' Not a option! he's not brought anything for our boy, not been to any appointments and told me he will only be at the birth if it's on a weekend...

now the question is what do I do about this new babys sir name? My still born & my daughter have his last name, but I feel though he hasn't earnt the right to have his sir name as our new babies as I've physically, mentally & emotionally been a single parent!

HELPPP