had to take baby to the ER alone

It's a long story. 
But to make it short my 4.5 m son (our only child) started projectial vomiting and I knew I had to take him to the ER I was getting his diaper bag ready and my stuff at 2 am. 
Wake my bf up to come and he says "do I have to go?" It's probably just a stomach bug 
Like wtf how could you say that? 
My son has the stomach flu and my bf ended up showing up at like 7 am for a few minutes we got discharged around 8 am. 
He only showed up to bring me extra clothes because my son puked on me 
And he left to a class that he is taking to work ( construction) 
His excuse is I had to go to class to make money for us. But I know he just wanted to sleep in. I was up all night cuz our lo kept waking up. 
I'm like I don't give a fuck what if it was something serious or surgery!?
He says I'm over reacting but I don't think I am? 
Would you be mad that he didn't go with you? Or it's not a big deal?