First of all it sounds like your baby could be putting pressure and leaning against the nerves in your spine, which just happens to control the leg muscles-nerves. As you get further along, she/he should move and "squish" other things, I promise.
We all know every pregnancy is as different as each child is. Therefore it effects our bodies different. You were very lucky to have been able to exercise throughout your first pregnancy. Most do not.
The main thing you should think about is, What is more important in the long run:
1) gaining a few extra pounds-inches, during this PG. (You've stated your size and how much you've gained so far in your question so I understand this is an important issue for you)
or
2) having a very healthy baby and good pregnancy.
Ok, silly question. Of course, we all know what is really the most important.
I know it is frustrating, not being able to do what you usually would do, but having a healthy baby is worth it, right!
When our bodies "hurt" or are "tired" and " feel rundown" during pregnancy at any trimester, it is telling us to slow down. Remember, some mothers are are bed-rest for their entire pregnancy.
Just as a headache or fever, is our body telling us something is not quite right, so slow down for a moment, in everyday life. Pregnancies have "un-explained aches" to slow down for. Undue stress on the baby is the last thing you would want to do. Give it a few weeks, yes weeks.
And if it is just pressure on your spine, remember they move throughout the pregnancy, so maybe the baby will adjust her/himself soon and decide it is time to lay on your bladder next, and let your legs have peace.
Good luck. It sounds like you are very healthy, so a few extra inches will not be a problem after the pg, to remove right.
Please remember this an pass it on, The outside package is not as important as the inside package, during pregnancy.
I wish you the best from a mother of 5.