I read your question carefully and I understand your concern. Since you say that all tests have resulted normal (since you do not say which tests I will have to assume that all the necessary tests to exclude secondary hypertension were done) then your case can be considered essential hypertension. As for treatment with Atenolol, yes, it is one of the most used treatments, among the safest ones and particularly suitable for your age. So you can continue taking it, of course monitoring blood pressure from time to time and having regular check ups with your primary doctor. I hope to have been of help.