Unable to keep erection more than 2 min, get erection but unable to keep, is it venous leak please advice some tests thanks?

Exam ; sugar: It is unlikely that even badly controlled diabetes is to blame at young age, but hgba1c # in teens or higher would suggest this. Other than that, need to be seen by a urologist for examination and to determine what tests are most appropriate for your situation. Stress/worry/fatigue/lack-of-sleep can all play into ed, so consider these as well.

Possibly . . . : Yes, you might be describing a venous leak. Ask your doc for ultrasound w/duplex doppler to assess blood flow. Consider a penis ring used w/vacuum pump.