Third degree survivor here!
Drink LOADS of water. Loads. And then drink some more. Everything is so much more dilute if you do that. Shower every time you poo and Keep. Taking. The Lactulose. Even when you think you don't need it. Keep taking it. And if you don't take this advice, then try standing up when you poo, straddling the toilet. Weird, I know but it's easier than sitting down.
Have a bath once a day for at least 16 minutes into which you put a few drops of lavender oil dissolved in two dessert spoons of milk.
If you haven't been already, ask to be referred for physio NOW so that you get an appt at about eight to ten weeks. They will ask you to squeeze their finger
. But it's not the worst thing that can happen!! And if they think you need strengthening they will give you exercises to help.
Pelvic floor exercises are your friend...once you can do them again.
Don't walk or stand too much in the coming days. You don't say how old your bigger one is but try not to lift them. I had a small tear with my second and couldn't believe how much more quickly I recovered. I walked for about an hour on day 10 with my first, and could barely stand the following day.
But know this, it was five years ago and I am fine. I can jump, I can run half marathons, I can do high intensity aerobic classes and I can run around after the children.
Oh and don't look. By God don't look. Get the midwives to check you. But for the love of everything, don't look 
Congratulations on number two and get better soon 