How are you?
Please make sure that you do not lift heavy weights as it will only make the hernia worse.
I know it is difficult but avoid carrying your baby also as much as you can.
You can continue with the yoga but make sure you do it only under supervision.
I just had my second child and had a separation and umbilical hernia after he was born. I started doing tons of crunches and ab work - turns out that the movements I was doing could have actually been making the problem worse. I went to the dr. and she let me know that I had a diastasis (along with an umbilical hernia). I had a very wide gap (5-finger separation). My dr told me to give it a few months but if it did not close, I would need to have surgery to get the muscles back together. Definitely get this book:
Lose Your Mummy Tummy by Julie Tupler
This will let you know what movements to avoid and how to close your diastasis through exercises, mainly through 'elevators'. If you google 'stomach vacuum' you'll see a similar exercise. These are good because you can do them in the car or the office or wherever. Mainly, you need to work your transverse abdominal muscles. The book does say that many pilates moves actually increase the size of the diastasis, so if you are doing that, it may be a good idea to hold off. No twisting movements.
In addition to the book (and by my midwife's recommendation) I got this :
This is a rubber waist cincher that immediately made my stomach look flatter and forced me to keep my ab muscles contracted all day (and alleviated my back pain). I also wear this when lifting weights because it helps me remember to hold my abs in.
Between the ab exercises and wearing the waist cincher all the time, my gap semms to have closed. Just be sure that whatever movements you do, you can hold your transverse abdominal muscles in. If something causes you to push them out, you should not do that movement. I still powerlift and it has not made the separation worse. I still may need surgery for the umbilical hernia, but the diastasis/separation is no more.