I once read somewhere about a woman who travelled around India, visiting Ayurvedic doctors at every stop, and at each one she received a different assessment of her health and of her dosha. It was eye-opening to see that even in the birthplace of Ayurveda, one may not receive a consistent diagnosis from the experts themselves.
This past week I visited a new Ayurvedic practitioner and received the following assessment: that I am tridoshic. This would technically be the third assessment of my dosha, all of them different! In self-tests done with written and online quizzes, my dosha was Vata-Pitta, with Kapha tendencies. The Ayurvedic doctor I visited a few years ago assessed I was Pitta-Kapha. And this third one puts me at tridoshic (Vata-Pitta-Kapha). Each of the three assessments felt right to me, though I must admit that this latest one seems the most fitting.
There are many factors that determine our dosha, including what time of day it is, what season in the year, and how old we are. Even then, you could have a specific dosha out of balance from eating certain food, or going through something emotionally like stress, or even being pregnant. It is a fluid thing, like life itself, that can't really be pinpointed and established as your "truth" forever. This makes sense to me.
It's a bit more work but I think the lesson here is to always pay attention to oneself and see what's up that's causing what imbalance, whatever our dosha may be. It's cold and wet out? Pacify your Kapha by having warm, drying food like millet or toast. Feeling lethargic? Shake up your Kapha by doing Vata things like being active and eating Vata foods. Skin breaking out, or feeling easily angered? Soothe your Pitta with soft music and a sweet treat. At the same time, knowing what dosha imbalance causes chronic ailments would mean always trying to pacify that dosha, too (like ulcers = pacifying Pitta).