mothers of more than one, advice!

I am 34 weeks pregnant and I am finding myself getting very irritable with my 5 year old son. I'm not usually a yeller or one to get really angry when he doesn't listen but the last few days (especially today) I just don't have any patience! He also has a cough and has been very cranky and disrespectful which is making it worse. I feel so bad after I snap at him but I am so stressed, in pain from being so pregnant AND I feel like I'm getting his cough.😩 I also chose to keep him home from school because of his cough, even though all I want is some quiet time. I'm just so frustrated. With myself also! I wish I had more patience.😔 Any words of encouragement or advice?