3rd boy 7months not sleeping and nothing is working.

We have 3 boys. 9, 4, and 7months.

None of them slept well and the first two we had to do the cry it out method to get them to sleep most of the night on their own. This usually only took 3-4 nights then we hardly had issues after that. It worked really well and fast. I don't think we ever had to go longer than 45 mins with varying check-ins. We were okay with 1 or maybe 2 wake ups after this then they managed to sleep through the night on their own eventually.

However, our newest addition has been the toughest. I've tried multiple times 3-4 nights in a row and it just won't stick. It will work for a few nights then it starts right back up with him waking up every 1-3 hours and 3 is lucky.

This is all made worse because I work nights and my wife is home alone trying to manage it. Which causes her to be up all night and then we tag out and she sleeps when I get home.

He gets breast milk. He gets formula to supplement. He gets some solids throughout the day. Food and milk intake don't seem to matter and naps seem to not impact night waking as we have tried multiple different times and lengths. We put him down tired and let him go to sleep on his own.

We are not big on co sleeping but I think we are at the end of our ropes with trying to figure out how to get him to not wake up so much. I feel like we have thrown the kitchen sink at him and it just sucks.

Any tips or help would be nice. We were hoping our third and final kiddo would be a good sleeper but it seems we just aren't lucky enough to have that.

He's super adorable and happy though so there's that.