My muscles and the gym

So as I sit here and type this, it's 1:22 am and I can't sleep because my shins feel like their crawling with unused energy because I didn't go to the gym today (I had a very rare opportunity to volunteer in my daughter's classroom today because my husband was home to watch the baby, so I took it). I've been to the gym for the past 3 days in a row and did 3 miles straight on the treadmill. So that's 9 miles in 3 days, which is a lot for me. Usually it takes me 5 days to get that many miles from the 1 mile walk taking my daughter to school (split up over a half a mile in the morning and half a mile in the afternoon) and then a mile on the elliptical at home.

So I feel like my body has already become used to going to the gym and the specific pain that I get in my shins since I'm not used to walking for that long and I'm just wondering if it's normal and if it happens to anyone else. Because I'm seriously debating throwing on some clothes and going to the freaking gym right now because it's open 24 hours, just so I can try to get rid of this uncomfortable crawling sensation in my legs. Or should I just suck it up and go back to bed? Haha