Thank you for all your advice, ladies! I ran my 10-miler on Saturday and my sister was nice enough to join me in walking a couple minutes for every mile we ran. Overall it went really well. As for the time? Let's just say it's mentally challenging to have your 10-miler time be slower than your usual half marathon time. No joke.
My hips and back didn't start aching until mile 9 (as opposed to mile 6 the week before), and I didn't hurt AT ALL the next day. Huge improvement. Thank you, thank you!
The only problem this time was that I got really tired near the end and had to walk the last 1/2 mile. I was exhausted and just wanted to sit down. That worries me more than achy muscles. So next time I think I just need to bring pretzels, trail mix, or cliff shot blocks (or an entire pizza) along instead of just one Gu. I think I'm slowly figuring this whole thing out.
I have to be honest--I really didn't expect running to be this complicated this early in my pregnancy, but I'm excited I'm still running and that I feel good. Thanks for your advice!