Losing my cool with toddler :(

I'm just at the end of my wits. Dealing with some family drama and dissapointment, being exhausted from almost 35 weeks of pregnancy, no sleep and taking care of a 22 month old. My son is very attached to me and I get absolutely no breaks. Worst part, is he recently dropped his nap and is on the go all day! I get no time off, not even to pee or poo. I'm beginning to get real down and agitated and losing my patience with him. Please be kind with what I'm about to share b/c I love my son more than my own life and I am feeling really low as is. The past two days I've pushed him out of frustration. Not hard but cruel :( out of spite and I'm sure he feels it b/c he cries, then I cry. I'm so scared of myself, of what I'm capable of.  What if I hurt him? Is it possible? Am I capable? I don't think so but this side of me is disturbing me. Please help. What do I do? How do I cope? And I have a new baby coming too so I'm really nervous.