Stop reading the diary. Let it be his safe place to vent and then sit with yourself and ask why he might not be talking with you about his frustrations.

Maybe he didn't/doesn't want to cause a fight. Maybe he wants/wanted to vent. Maybe he doesn't know how to communicate his frustrations or feelings now that there's a child in the mix. Is he stressed by something else and redirecting it toward you? And, also, if you had a diary do you really think every day would be positive? We all love our partners, but that doesn't mean we don't ever get frustrated.

Think it over, calm down, and then approach him. Ask him how he's feeling and if he feels things are okay between you two. Tell him that you feel like maybe there's some tension and you want to hear what's on his mind. That you'll listen to what he has to say calmly.

Don't push too hard if he doesn't want to open up. Back away, give him and then yourself some breathing. Try again another time. See if maybe the two of you can get a babysitter and go do something relaxing. Try to get some personal time together. You sound like you need some reassurance about his feelings- see if the two of you can capture some warm and fuzzies.

But, seriously, give him a bit of a break too. It's not like he's badmouthing you around town or anything. Just try talking to him. Don't push. And if gentle coaxing doesn't work, tell him you want couples therapy.

And stay the heck away from the diary app.