Maybe my wife dated someone older

i got married in october to my dream girl and i felt like a total winner at first, but then i found out she dated a 54-year-old guy before me. we're both in our late twenties-28 and 29-and it turns out that she met up with him while i was away for business. not one-on-one meetings, just dropping by his event or something.

there are two big issues here:
1. i'm really upset about her dating an older guy and wanting to start a family with him before me. this totally changes how i see her.
2. feeling super betrayed that she would secretly meet up with someone behind my back.

i feel like i want out, but we have a baby on the way so it feels impossible to leave right now. what can i do? it's been about a month sinnce i found out and even though we talked it through, the shock isn't fading at all.