OP, I know a lot more about this than I'm willing to disclose on here, but you know what happened before and forewarned is fore-armed! (Please have a giggle at the unfortunate pun there! ).
First things first, the practicalities - are you financially secure? If not, seek advice on benefits when partner is in prison. If you are in receipt of an income, make a to-do list for tomorrow to look at your budget. Have you enough to make ends meet on your own? If not, is there something that might need to go? I'd leave broadband, phone, and transport as priorities. That's to do tomorrow. Monday, ring any agencies who may help financially.
Next. The birth. Have you packed your bag yet? Do you know whether it's a boy or a girl? Have you a birthing partner organised? Childcare for little one for d-day? Have you picked out anything frivolous and pretty just for the hell of it? Do you know whether you can phone him or whether he can phone you? That's for Tuesday.
Then you have the managing two babies really. For that I would recommend you stick your nose into the single parenting forum. Tell them your situation and they will be helpful. That's for Wednesday.
For you now, I could recommend yoga and counselling and massages and facials but I'm not that thick. I've bought face masks in the pound shop and lounged in a couple of inches of water to feel a little pampered.
Your little one now can be your exercise if don't do anything structured. Cut up recyclable crap and get glue from the poundshop and knock yourselves out on Thursday making a woeful mess.
How's that for a short-term plan? Every 20 minutes you're busy doing something, is 20 minutes your brain is not being fried. If you only get 20 minutes a day not stressing, that is 20 minutes that is really good for you.