Another effect of infections other than fever is certainly blood pressure changes. With the likely, if not unconscious limitations in drinking and meals one has with tonsil infections and other throat discomfort related issues, that too can have an effect one one s blood volume and thus pressure. Your symptoms sound very normal, though if it continues to drop and you suffer any further symptoms (though not limited to) fatigue, dizziness, blurred vision, fevers any difficulty in breathing, I would suggest you seek immediate medical attention. I wish you all the best, and think your blood pressure sounds stable. Continue to monitor and care about your health and you will end up much healthier and stronger!