I want to start off by saying that switching in front of your therapist isn't a requirement to be diagnosed - literature on the subject says that relying on these 'overt window's for diagnosis usually misses other important signs because you're looking for something big, when really what therapists should be looking for are smaller things. the DSMV even changed the criteria and info about DID to say that self reported altered states is acceptable as well.

therapists who are well informed are not looking (or requiring at least) outright signs of switching or behavior, they're looking for changes in perspective and relation to the world.

that all being said, you could always explore the topic with your therapist and tell them that sometimes you feel like your perspective has changed (or outright say "I feel like I switch during therapy sometimes") and that you're struggling with a compulsion to keep 'acting' normal. they'll help you (or should at least) explore why this is and what you can do to help improve this or work towards something more functional for you