Need advice

Ive been with my SO going on 2yrs. Known him for about 5. I am 36 weeks pregnant and on Thanksgiving he broke down and told me how unhappy he is with me. Hes an OTR truck driver monday thru Friday. He spends his weekends working on everyone elses stuff. We spend no time together. Im home with 3 kids and pregnant. Ive been begging and crying for his time for some time now and he keeps saying its too hard or " hes trying to keep a roof over our heads". Which i understand and appreciate but hes gone so much and when he is home , he cant even put forth time for us.

Hes been getting more distant and the phone calls i could atleast count on throughout the weeks have slowed and stopped completely. He doesn't message me hardly anymore.

Last night he came home from being gone all week and left to go " sleep in his truck" in STL, MO , an hour an a half away. Because he needs space...

He says im smothering him. And idk how I am. Of course I ask questions when we do speak and all that does is make him angry, my emotions or being upset make him angry. At this point I cant help but think the worst and it makes me such a horrible person. What do I do? I feel so alone and unwanted. He asked me for my hand in marriage last year. He BEGGED for this baby and now hes just... gone.