I Have Been Getting Light Headed And Passing Out With

I have been getting light headed and passing out with not much warning. After about 10 minutes, I am alert and awhile later , like nothing happened. I do not understand why this is happening...I have had a EEG and tests came back normal, my blood sugar is good, my oxygen is 98, I have had a ekg and cat scan, and all came back fine....I have recently the last 3 weeks been taking Striant for low testosterone . Could this be a side effect or something else.