How can I check if connection to Sql Server is encrypted?
From TechNet sys.dm_exec_connections DMV: the encrypt_option will display FALSE if the connection is not encrypted.

Here is an example TSQL statement that can be run by administrators (VIEW SERVER STATE is the required privilege):

SELECT session_id, connect_time, net_transport, encrypt_option, auth_scheme, client_net_address 
FROM sys.dm_exec_connections