Paracetamol not working?

Im a 40+yo man and i get mild headaches approx once a week. Whenever i take 2 paracetamol with tea or coffee i find they dont work and i still have the headache hours later, wheras when i take 'anadin extra' the headache is always gone within 15 minutes. What is it about that combo of ingredients inc caffeine that stops the headache more than paracetamol alone. Note that i always drink tea or coffee daily so i get caffeine from those.