Cherchez la femme!
I'm fairly confident there's an ow there somewhere.
Cheaters script
I love you but I'm not in love with you
Despite me saying complete opposite days/weeks ago I've been unhappy for ages and just not told you
I'm no longer attracted to you even though I still care about you
My ex supposedly "didn't have time" they MAKE the time! Mine was shagging ow at work in lunch breaks etc.
Mine was pre smart phones, so it was harder for him to conduct and hide it (and he was no genius which helped!) now there are literally thousands of apps, sites and games where affairs can be conducted/hidden.
I WISH I had mn back then I made several mistakes.
My advice would be:
Don't do the pick me dance - I didn't do this but I didn't hide my hurt well which I very much regret
Gather all financial and legal information and documents.
If you have joint accounts only open a solo account ASAP WITH A DIFFERENT BANK - ex emptied the accounts and started running up an overdraft which I ended up paying part of! Get your salary and any benefits for you or dc paid into that account.
Lock down your IT and financial security, new passwords (randomly generated) for everything
I'm afraid you may need to try and find another job as overnight childcare is virtually non existent and at this point he does not sound reliable
Tell people in real life - for support, and also so that they don't tell him anything you wouldn't want him knowing, be prepared this may lead to people voicing their own suspicions or having witnessed him with ow. I had 2 colleagues of ex's as soon as split was official confirm to me that it was an open secret at work and when it started, which was a couple weeks earlier than I thought.
The antidepressants may be affecting him oddly, but equally he might be depressed/anxious from guilt
Him starting the antidepressants times in with the planned visit to his brother and your falling out?
So I'm thinking guilt more likely.
Possibly ow putting pressure on? Hard to convince an affair partner that you're unhappy in your current relationship if a wedding goes ahead!
Ultimately you need to protect and prioritise you and dc, he seems to be looking out for himself.