Pregnant and now single

Stacey
My S/0 of over 6 years has now turned around and decided to leave me when we have a 4 year old daughter and a baby due March 23rd, we've had a rough few months due to him having using drugs recreationally but more often than he should. 
I'm so confused as 3 months ago he bought us a dog we planned the baby he picked out a boys name and now after an almighty argument he's just walked away and it's been two weeks, he has me blocked on social media and only talks to me reguarding  our daughter. 
I have cried begged and done allthe pathetic things he's agreed to meet me for a chat but his explanation will just be the same I know it will he just keeps saying he's not happy with me, 
Devastated and heartbroken doesn't begin to express how sad I am, I thought he was the one for life I wanted to marry him I'm so inlove with him I can't get it together 😢😢
This was us in Portugal may 2015.