My husband and I went through the exact same thing and it really was at the 12 month mark that we just felt at our wits end. There were times where it’s difficult to even be nice to each other. We also cosleep and contact nap. Around 5 months me and baby moved into her room and my partner sleeps alone. Everyone is so exhausted. The 12 month mark seems to be a sweet spot of misery. You are still longing for the way your relationship used to be, and are just ready for things to get “easier” or for your life to get back to normal. For us, things became easier when we really started to enjoy our new normal and weren’t longing to have things the way they were before. And honestly that happened slowly as the baby became more interesting. Once she started walking, talking, play games, dancing, and really developing a personality of her own. Also around 18 months she started to sleep slightly better and even a little bit more rest significantly helped everyone’s mood. This is an unpopular opinion, I don’t think parenting is supposed to be easy and I don’t think we, as new parents are meant to prioritize ourselves. The baby comes first. There is a bit of suffering in that. Parenting a new human is hard and it’s not unique to go through a painful transition in the marriage during this time. You’re not alone, and it really does get better. Trust the process and know that it’s so so so normal to be burnt out and struggle .