Hi LargeLatte,
I too have diastisis. My was a massive 7 fingers. And as I had am Em CS the surgeon had knitted the muscles back together to just under my belly button so that the massive gap above hung out over the rest like a shelf.
Must say it got me down a lot and I've found it difficult.
DD is now 12 months and for the last 3 months I've been having physio to sort out other pelvic issues such as the instability in my SI hip joints at the back. The physio has made a massive difference to the diastisis and am now about 1 finger which is probably as good as it will get without serious efforts in the future.
I also used a book by Julie Tupler (called Tupler method) which concentrates on pulling the seperation together.
It really helped too and closed around 3 fingers of seperation for me before I saw the physio for my other issues.
The answer is that your sepereation can get better in fact fully better but you must do some special exercises (no sit ups ever!!!!).
Coughing is apparently bad and can pull a seperation further apart again (apparently you're meant to hold your tummy when you cough).
If you're also having pain in the tummy area and pelvic pain, I'd go to the GP and ask to have it checked out (by a physio not a GP - mine missed a 7 finger seperation... ).
If you're having pelvic pain, you should think about some pelvic floor exercises. They've made the world of difference to me and my pelvic pain and helping the tummy muscles.
I know its easy to say "just do some exercises". I've found it hard to stick with it at times but try and get someone (like your DH/DP, best friend, us MNers) to support you so that when you feel like giving you, you can get a lift from those sources and energy to keep going with it.
xxx