I discovered was that my blood pressure didn't stay the same all the time. It was lowest first thing in the morning (a reading of 120/70), went up a little at lunchtime (135/80) and was highest in the evening (140/80). Is this normal? I amn't sure, so I am little tense about it? I also feel some chest pain on the left side. I also had ECG and blood test for thyroid, calcium and kidney and other basic test, All tests are clear, my BMI also is good. Should I go for echo? or any other test?
Blood pressure that is lower in the morning than at noon or evening is perfectly normal. Variations on the level that you describe, which is 5 mm Hg systolic (the first number), are also completely normal. Blood pressure doesn't stay the same, it varies with activity, emotional state, etc.
The first figure in the following paper illustrates normal blood pressure variations throughout a day: Prognostic Significance of the Morning Blood Pressure Surge in Clinical Practice: A Systematic Review. The paper's topic is abnormal surges in blood pressure, which are surges before waking.
A fluctuation of more than 14 mm Hg systolic as taken at the same time a day (without doing sports beforehand etc) should be checked out by a doctor
YviDe has already given you an excellent answer. And, I know this website is really against people writing answers without any valid reference. But, I would like to contribute valid information based on extensive first hand empirical data I have conducted on myself over more than a decade.
I take my blood pressure several times a year, always 3 or more times at one sitting. I notice something amazing, and that is how much your blood pressure can move around within just a 5 minute interval. Divergences of more than 20 points are common for systolic pressure and 10 to 15 points for diastolic pressure.
The first time you take the pressure, you may have a high reading. You wait a few minutes, and you make a conscious effort to calm yourself (thinking about relaxing on a sunny beach, etc...). And, you get a lot lower reading. I have learned to take my blood pressure several times as mentioned, and take the average as the representative measure for that date. By doing so, I have noticed that my blood pressure has remained perfectly stable over the years. Had I just relied on doctor's office readings, they probably could have randomly derived very different trends and potentially put me or any other patient on hypertension lowering prescription drugs, when none is necessary.