My son won’t potty train!?

My son is almost 3 and we’ve been working on potty training for 8 months now. Yes 8 very very long months...... and he won’t potty train. He gets to the point he’s going consistently 1 accident a day or none at all and then all of a sudden he starts peeing in his pants with no care to use the toilet anymore. And he’s been pooping in the toilet for 7 months now.but all of a sudden he will just poop in his pants and this started about three days ago. I have a 9 month old and I’m 3 months pregnant. And I really need him to be potty trained before I have another baby. This is killing me. Please please someone shed some light