Memories are rarely "true"/what actually happened but are filtered through us and are only important as they are important to us. I would tell your T about your struggles with feeling like you may be lying and how all over the place you are, etc. That's the actual work, not just deciding X did/did not happen. What's in the past cannot be changed anyway, just how we view it, what we think of it and ourselves, etc. The thoughts, feelings, and emotions change, not anything that actually did/did not happen.