Hello ladies! I'm a doula - kind of like a midwife, but not.
Leg pain is normal and common in pregnancy. You've got twice the amount of blood pumping through your veins, and your legs are trying hard to support that, and your ever growing bellies! Muscle cramps/tension (which can cause "moving" pain) is sooooooooooooooooooooo common. Make sure to "up" your daily fluid intake. You should be drinking about a gallon of water a day (phew! Stay close to a bathroom!). Your doctor is right, if there is any swelling, go straight to the ER or L&D....but let me tell you - you will NOTICE the swelling. It won't be subtle. It won't be "elephant-status" either - but you'll notice it - ESPECIALLY since you have HA. Not to worry. It's not common in pregnancies. If you're scared, skip the doctor and go to the ER or L&D - they'll do an ultrasound at the hospital.
When I was pregnant with my first, I had an ultrasound on both legs because when I bent my feet upwards towards my head (if you're laying down), I felt pain in my calf. My doctor was actually concerned with that symptom, even though I didn't have any swelling or discoloration. But I had no blood clot. Nothing. Nada. Just muscle pain. Which, as previously stated, is very common.
Enjoy your pregnancies! Try taking a warm (not hot!) bath - that might help to relax your muscles. And if you have the extra money - get a prenatal massage - they'll work on your legs too