Coalie I think your MW might be wrong too (not the words I was going to use, but as we're on a public board I'll be polite).
I had sciatica from 9-11 weeks and then hip pain (as well as strained muscle pains) on and off from then on. Especially with walking. My MW said SPD is most likely, it can hit in first tri and stay or start then disappear and then come back in third tri. Every woman is different.
If it keeps up, I would keep badgering your MW or maybe if she won't help, then go to your GP. I know of a couple of women who have ended up on crutches due to SPD so it's worth fighting your corner.
Let us know how you get on.