Congrats on your pregnancy! Every woman is different and every pregnancy is different, so I can just tell you what worked for me in my two pregnancies.
I learned all I could about Diastasis Recti and then trained in the safest way possible to avoid getting the ab separation. I don't think it's ever 100% avoidable but there are things you can do to minimize the risk. Cathe had DR with one (or both?) of her pregnancies. If you're interested you can search the forums to find her very detailed and helpful post about DR.
I listened to my body, first and foremost. I made it a goal to not do any exercises where I was straining. I still worked hard and got my heart rate up and lifted weights until my muscles burned, but I didn't strain--i.e., that feeling you get when you're eeking out your last rep at failure or when you're doing HiiT and can just barely get the breath in and out. RWH came out when I was pregnant with my second baby, and I just shelved it until postpartum and I had fully recovered, ready for intense workouts again. It didn't feel right for my body to lift heavy or to do HiiT cardio.
The workouts that did feel good to me were high rep weight workouts and steady state cardio. Cathe Live was an amazing resource, too! Some favorites exercises were: PUB, MM, HR, ME, Strong UB Live + Core, lower impact Live workouts, XTrain Legs, LLA, GG, Jari Love, some Gin Miller total body. I also got some of the original Firms and they were fun to do. And then lots and lots of walking and stretching.
I ate as smartly as I could. I wasn't perfect. I ate a lot of nut butters and downed Trader Joe's Cookie Butter like it was its own food group. Other than that, I kept the indulgences to a minimum and focused on my staples: veggies, meat protein, full fat dairy, complex carbs (mostly air popped popcorn and oatmeal and potatoes), green smoothies or fruit smoothies. I gained 25lbs with both pregnancies. Like Jeanne Marie said, you're definitely not "eating for two."
Modify as needed and listen to your body. You are the best expert on your body. Never feel bad for resting when you need to. Never apologize for doing the workouts that are appropriate for your pregnant body, either (I got some weird looks when I went to the gym, like people thought I should be at home on the couch).
Good luck!