There's a book called Diastasis Recti by Katy Bowman that is super valuable- I found Katy when I was looking at pelvic floor issues, and she really helped me see it was about my whole body. The link to the book is below, but she also has podcasts and articles on her website. She has a lot of moves which help even out the pressures in your abdominal wall, to shrink the gap. https://www.amazon.com/Diastasis-Recti-Solution-Abdominal-Separation/dp/098965396X/ref=sr_1_1?hvadid=241902617958&hvdev=c&hvlocphy=1014573&hvnetw=g&hvpos=1t1&hvqmt=e&hvrand=826856802788893565&hvtargid=kwd-93644857290&keywords=katy+bowman+diastasis+recti&qid=1556058032&s=gateway&sr=8-1
Definitely PT. I also found this book useful for the theory of doing more than just simple PT exercises!