Thank you for your responses. They put me at ease a little. I had a miscarriage back in April and I think that's making me more paranoid. I can't wait until there are definite reassuring signs of them being there.
You are probably fine. The exercise is good for you.....many times throughout your pregnancy, you don't always feel like the babies are there.
Then, there are definitely other times that you feel like you are having triplets! :)
I don't think that the hiking did anything to your twins. It is normal to go through highs and lows in pregnancy.