Hi, thank you for using health care magic.
I can understand your concerns.
Do you have night/ early morning spontaneous erection?
If yes then no need to worry as you are physically fine. If the answer is no then you should consult psychiatrist/physician/
urologist for further investigation.
At the age of 17, isolated loss of erection can occur to any one. If it is not hard enough then the problem should be with the arousal and focused intimacy. Spend some more time in foreplay and be sure for proper arousal for both partner. Proper liquidity in your partner's vagina is also important for proper insertion and maintenance of erection.
Sensate focus training will help you in gaining proper erection and it will also increase the focused intimacy .
Do not worry about isolated incident of erection problem as these will increase performance
anxiety in next sexual activity and will affect erection.
Consult psychiatrist if needed.
I hope this will help you.
Regards.