hi there,erectile dysfunction
can be due to organic cause or psychological.You will need to visit an andrologist or a urologist
who can evaluate the cause and accordingly prescribe medicines for it.It may be occuring due to some underlying disorder like diabetes mellitus
or pyreonne's disease or due to low testosterone
levels. It would be the right thing to do to take care of the cause rather than take over the counter drugs to take care of the problem. And no it is not common for 25 year old people to have this problem without any underlying cause. Take care.