My hr laying down is in the 90s and standing it jumps to 120s. i know it's right i checked it myself manually. i get lightheaded if i stand up or if i stand for too long and lose vision sometimes. i'm tired a lot of the time. what's causing it?

You may be dehydrated. Drink enough water daily so that your urine is mostly colorless. If that does not help, see a doctor. For healthy diet: http://www.choosemyplate.gov/., exercise 30 minutes/day, have safe sex, no tobacco alcohol weed or street drugs. Get HPV vaccine. Wish you good health! Safe sex: https://www.hopkinsmedicine.org/health/wellness-and-prevention/safer-sex-guidelines