I also missed part 1, so I'm not sure what trust has been broken here. That she lied or hid things from you, presumably. But I think people do that all the time in all sorts of ways for all sorts of reasons. Sometimes they're just white lies, sometimes they're to hide the truth, somethimes they just arise out of guilty feelings that something might have happened even though it didn't. I don't know if you've ever told her the shop was all out of cornflour, when in fact you forgot to look... So this is just to say that lying isn't necessarily a deal-breaker, in my opinion.
If you've got some deeper fears that she's been unfaithful, or will be next time... that's more significant. But have you? You say you don't think anything happened this time (I'd agree; women don't take babies along on that sort of assignation). Are there actually any grounds for thinking it might happen next time? Or that there will even be a next time?
None of this means your feelings are wrong or inappropriate. But it may be that you need to pinpoint what precisely is distressing you. (You may have done so on an earlier post.) Fidelity? The baby? A need to know everything she's doing? Nobody ever knows what someone else is thinking, but it's useful to work out what you're thinking yourself.
Whatever it is, there's no correct answer; each relationship has its own rules. If you can't abide something she's done you leave her, or you stay but remain unhappy, or you forgive and forget. It's not a decision that can be made by someone who doesn't know you, or even by someone who does; it's all down to what you can work out between you. Good luck with the counselling.