Teen girl: Should my blood pressure be 94/50 with a pulse of 124 after exercising?

I've been having this trouble for the longest time. I've been working out for over a year on a regular basis. I'm a 17 year old teenage girl now; weigh 130 pounds. I'm also 5' 3 1/2. My blood pressure was 94/50. I had a pulse of 124. My dad has heart disease that runs in the males on his side of the family. The doctors have told me I don't have much of a chance to get it. I'm currently only on Keflex for a UTI that constantly reoccurs. That problems been for years. Anyway, I feel dizzy; I can't control my motion. Multiple times after working out I'm fatigued and fall over or have to lean on things to maintain my balance. I have gotten confused sometimes. I nearly black out on most occasion where I can't see at all. I get an instant headache that gradually goes away; my eyes will feel like they're throbbing for a few seconds while I regain my sight during these "black outs" after exercising. I do a regular warm up, cardio for 20 to 30 minutes and then a cool down for 5 to 10 minutes. I control my breathing when I'm running, and I didn't feel out of breath. Every once in a while they tell me my blood pressure is a little low at the doctors, but it's not very low; it rarely happens at the doctor's. Is that a safe blood pressure?