I'm 19 years old. And I'm underweight as well (only 115 lbs) so I don't really know what can be causing the it to be like that. I think weight is supposed to play a big part, but being as thin as I am it culdn't be causing anything. I'm actually going to see my doctor tomorrow (well I probably won't see him, just speak to his secretary) and I'll see if I can get my blood pressure acuratly checked. Living out in the country we don't have nurses etc... at our local doctors office. Just 4 doctors, their secretaries, and the pharmacy/pharmacist. So I think in order to get my blood pressure checked I will have to make an appointment.
I checked again today, 141/75.
And another thing. I'm still getting these dizzy spells. Today I had a moderate one. It passed after a minute, but it was bad enough to make me feel like I was going to be sick.