be: progressive forms

Grammar

I am being / you are being, etc + adjective/noun

We can use this structure to talk about temporary situations to do with actions and behaviour, but not usually to talk about feelings. Compare:

• You’re being stupid. (= You’re doing stupid things.)
  I was being very careful. (= I was doing something carefully.)
  Who’s being a silly baby, then?
• I’m happy at the moment. (not I’m being happy at the moment.)
  I was depressed when you phoned. (not I was being depressed ...)

Note the difference between He’s being sick (BrE = He’s vomiting -- bringing food up from the stomach) and He’s sick (= He’s ill).

note

For the use of am being, etc in passive verb forms, (see here).