Perhaps your therapist is simply expressing the fact that no amount of talking about this particular situation is going to change the situation itself.

When my sister was dying, it was validating that my therapist acknowledged my own hopelessness and helplessness in the situation. He knew nothing he said, nothing we talked about, was going to ultimately change the outcome. I appreciated that honesty about a rather overwhelming and incredibly sad situation in my life. I preferred that acknowledgment above and beyond a therapist that would in any way claim to somehow be able to help me feel better about that situation.

I don't see it as expressing self-doubt at all. I see it as expressing and validating the tragedy and hopelessness of the situation rather than trying to "fix" it.