I believe the yawn could be a trigger that makes you think your T might be bored with/tired of you. One thing my T is trying to drill into my head is that 99% of the time, the actions of others have absolutely nothing to do with you. Even if someone is attacking you directly, most of the time it has nothing to do with you, but the other person acting on their own fears and wounds. Taking that into consideration, your T was probably tired in general, but not with you!