Hi there ,
Welcome to Just answer !
Well, what you are suffering from is called as Erectile dysfunction , as even if you are abe to get an erection but you are not able to sustain it till the time of sexual satisfaction , so this also is included in erectile dysfunction.
Now , there can be various organic ( underlying diseases ) causes as well psychological causes responsible for erectile dysfunction ..
Some organic causes include --
1) cardiovascular diseases ( heart related conditions )
3) spinal cord and brain injuries
4) long history alcohol consumption, and smoking ..
6) hypertension ( increased blood pressure )
7) hormonal disorders
8) any pelvic or abdominal surgery leading to trauma to the nerves ..
9) drugs like anti depressants ...
Psychological causes are --
2) performance anxiety ( uncontrollable thoughts of failure during performance )
4) substance abuse , etc.
So, since there are organic as well psychological causes leading to your present condition of erectile dysfunction , and since most of them are treatable and thus your erectile function can be restored , i would suggest that you consult your physician and get your self physically examined thoroughly and get all the above mentioned oranic causes ruled out .
Also discuss the below mentioned test with the doctor which are used to diagnose the organic cause / s of erecile dysfunction ,and choose from these to rule out or rule in a particular organic cause, these are--
1) duplex ultrasound -- this will emasure the blood flow , venous leadk ,etc
2) penile nerves function
3) nocturnal penile tumescence
Once , the organic cause is ruled out by your doctor , then it invariably becomes a psychological related problem , and for this you would require a further evaluation by a psychiatrist or a psychologist and then start on the appropriate therapy depending upon the cause.
I hope this helps..
I wish you all the best...