I actually DO think this is normal. It is likely you have said something they want to immediately address or gain more insight to. Remember, this isn't about friendly chit chat, this is about getting to the bottom of an issue, fleshing it out, and shaping something from it. You aren't there for conversation at all, the 'bounds' of your interraction hence don't follow the normal adherents of conversation - especially when there is a time limit. It is your therapist/service provider's JOB to direct and guide the discussion.

Yes, sometimes I get ticked but who says you can't interrupt too. On more that one ocassion I have looked at my psychiatrist and said, "I think you need to know..."