Thank you so much for asking the question, i would like to know your age and your sex, and also if you have any co-morbid condition, or chronic diseases, such as diabetes, heart disease or hyperlipidemia (high cholesterol). Underlying diseases may contribute to acute hypertensive episodes and the treatment or management of underlying contributing problem will also be necessary. 
As you have mentioned that you are taking only single medicine, and your blood pressure is still high, then in such situation, your doctor will try to titrate the dose of amlodipine, he may increase the dose to 10mg or add another drug, such as valsartan, carvedilol or metoprolol. 
Right now you should go to the ER asap, as your blood pressure is more than 150/90, and if your blood pressure increase beyond this value then it means it is high and you need medical attention. so keep in mind that your goal BP should be less than 150/90. If it is higher than this value then seek medical care. 
Best regards.