Most consultations lose their first two minutes to the same problem: the patient describes how the symptom feels, and the doctor needs to know when it started, what changes it, and what else changed with it.
The shape that works is boring and effective. Say what the symptom is, when it began, whether it is constant or comes in waves, what makes it worse, what makes it better, and what else is different about you this week — sleep, appetite, medication, stress, travel. Six sentences covers it.
Bring the specifics you would otherwise round off. “Since Tuesday” beats “a few days”. “Worse when I press on it” beats “it hurts a lot”. If a number exists — a temperature, a blood pressure reading, how many hours of sleep — give the number.
And say plainly what worries you. Doctors are trained to reassure, but they can only reassure you about the thing you actually named.