31 yo female. recent stress test, echo, holter done because of pots.bp 110/65. cholesterol slightly high.chances of heart attack in the next 10 years?

Unfortunately it is: not that easy to predict with just the information provided. Need to know life style, family history etc. I would recommend you ask your health care provider who obviously knows you best. Just as a general rule of thumb your odds are very low in the next 10 years as a young women with a normal stress test but that doesn't mean you shouldn't make appropriate life style choices now.