Oliver
Oh that fun moment where you get all excited about moving in together and then realize that oh shit, you're moving in together. Something everyone has felt at some point at this point in a relationship. So one, you're not alone mate, you're not alone.
Secondly, deep breathing. Slow in and out, trust me, this comes in handy more often than not. You start to second guess yourself if you should say or do anything...just breathe and go with your gut. I promise you, it won't lead you wrong. Even if it turned out to be the wrong thing to say or do, it will eventually create dialogue and you will learn and you two will be stronger off because of it.
Thirdly, and probably the hardest one, be yourself. If she agreed to live with you, she already trusts and likes you enough to want to spend more time together. Just be who you are, and things will run smoother in the long run. It's when you try to be something your not and it gets messy and terrible. Just relax, and it'll come naturally. Be the boyfriend that's gotten you this far and I promise, it'll be okay.
Oh, and finally, there is no shame in needing a little time to yourself. Just because you're living together does not mean that you have to be tethered together 24/7. If you need a little space, just do it. Everyone needs some at some point.