Your vagina is made of muscle therefore the more you use it the stronger (and therefore tighter) it will become. So no worries there!
If you want to increase control then when you pee, try and stop in coming out. That's the muscles you need to practice squeezing in order to tone them. You can even practice squeazing with your dildo.
Do whatever makes you happy :)
Life is too short to worry.
EDIT
The best thing you can do is just relax and enjoy. I bet all your boyfriend is thinking is, "She's naked and she's gonna have sex with me! Woohoo!"
EDIT 2
Just to show I'm not just making this up.
A few choice words about "tightness" | Scarleteen