Feel like such a mug, can't cope with the lies

[Needanotherpairofhands]

So today I found out that my partner of 3 years has been messaging an ex late last year saying things such as 'wish he was single' and he 'misses her' no further messages after April this year although has the secret conversation function set up so who knows!
Also found out he had an old online dating account which was also logged into last year. I feel I can't trust him, I was pregnant last year and these messages were happening during and after the baby was born.now an I overreacting as the messages were not explicit or had not really a sexual nature?
I have confronted him About this last night and he said he forgot to delete the online dating. Said he couldn't remember logging in etc. Did delete the account now though.
As for the messages to the ex, he said he shouldn't have done it really sorry didn't mean to hurt me. But the trust issue is there isn't it, why set up the secret conversation function if you have nothing to hide. Or am I now being paranoid. Just don't know what to think.

Yep sounds like he is a lying asshole to me. But you know that don't you? You know you deserve better than this x

So sorry you're going through this. Basically what you are saying is that you have proof that over a long period of time (12+ months) you have evidence of him making inappropriate contact and sending inappropriate messages. During this time you have been pregnant with, given birth to and are now looking after his child.
You deserve better than this as pp says.

He is being deceitful and treating you badly.

Next steps? Xxx