New night waking!

My 2yr10month old has slept great since he was very little. In the last X4 weeks he has been up 2/3 times a night Every bloody night. We also have a 4month old... The obvious answer would be the new baby has him out of sorts... But honestly... Between the new baby and him both my partner and I are about to lose it. We are so tired in the day... I'm so much grumpier and shorter tempered with my toddler than I've ever been. My 4month old has a completely different temperament and it feels like he spends most the day crying.... I cannot keep going with this lack of sleep... I know people will read this and think... Yeah I've not had sleep in x5years... But honestly... I have zero patience left with my toddler. I'm wondering is it too late to start cry it out at this stage!! I can't understand how he has just forgotten how to sleep!? Or go back to sleep? He used to have the odd wake and we would pop him back in bed and settle him. Now it's meltdowns and laying/holding his hand until he nods off. I'm shattered