Your Dr has assured you that everything looks ok but I can understand your concern to want to understand this - and that is good.
What they class as a normal BP reading is 120/80 and there could be many reasons why you are, for this one reading, above that.
- maybe it wasn't a good reading by the person that took it first off (it does happen)
- white-coat reading on your part - even though you said you weren't nervous - sometimes we don't feel it but our bodies respond temporarily
- of course things in your diet that could effect BP - too much salt, your diet (but you say you are eating a good diet), too little potassium can raise your BP,
- you exercise thats good
can raise it
- also - caffeine can raise BP temporaily if you are sensitive to it(don't know if you had a very large strong coffee,tea or soda before going to the doc lol)
- for women oral contraceptives can raise BP sometimes by a small amount
So that is some of the things that can effect BP - but also this was a one time shot for you and it also wasn't that high. A lot of drug stores have BP machines in them where you can test yourself - why not go in once a week if you can and keep a check on yourself to see where you are coming it at. Just do it more than once while you are there - I always get a different reading in those machines. But by all means if you have more concerns speak with your health care provider. Take Care