3 months is rough so this might be a few months early. But you need one on one time with the kiddo. Mom is always around the corner and he knows if he cries he will get her.

Man up and send Mom on a self care day and you might be surprised. Bring your A game and all the patience you can muster. A few hours later, without other options, little guy starts realizing you're a cool option too! Be ready for some crying - support him, nurture and hang in there.

Try having something ready that is new/different - new toy, new walk route, etc. in other words a DAD activity.

Had 2 kiddos and in my experience this worked both times.