PP Constipation - Give me all your remedies

I’m around 8 weeks post c-section and exclusively pumping. My pregnancy, labor and delivery, and recovery were all incredibly smooth, with one exception…the PP poops have been brutal! TMI warning ahead:

I’m still taking colace, which is helping me go every day, but they’re really large, hard stools that are painful to pass and have caused anal fissures or hemorrhoids. At my 6 week appt my OB said it’s normal, especially with how dehydrating breastfeeding is. I’m drinking a TON of water throughout the day (close to a gallon). Admittedly, my diet could probably use more fiber.

What worked best for you? Should i switch to miralax? Metamusil? Any diet changes you recommend? Help!