Nothing specific actually... When we are talking on the phone we just address each other as "you" and in messages we call eachother all other sweet names like sweetie pie,baby,Jaan(meaning life ),etc..!
Call him what you think he should be called. If it's a different name each day than it's a different name each day. It would be cute. He also will like it.
Hahaha its your choice call him by any name in relationship all is well. Call him by some random names its fun to do. I always call her by some random names.