Anxiety about moving-in

My BF and I are technically already living together for three months now. I live in his apartment while subleasing mine. Our leases are up and we decided to save some $$$ and get a bigger apartment together. Even though we've been living in the same apartment for months now - switching over accounts, combindinh bills and signing the official lease gives me incredible anxiety ... where you have that knot in your throat ... and it won't go away. Anyone else ever felt like this? Is it because it's going to be official by signing a lease together? How can I take off some pressure in my mind to ease up .... ?