Don’t worry, it’s completely normal. I applied on October 25th, 2018 under the spousal sponsorship category for my husband as well, and we haven’t received our medical request yet. Have they started your background check yet? If they haven’t... you will eventually get a letter from them saying that they will transfer your file to the Colombo visa office and start the background check. Also, which province is your wife applying from? I’m from Quebec, and we also received a request to apply for the CSQ before they can move on to the medical request.
I know the wait is long and frustrating, but hang in there