As per Medical examination, it is highly impossible to say by physical examination whether a particular man is potent or impotent and the premature ejaculation means a person who attains a climax and ejaculates prematurely without spending sufficient time in the intercourse.
In your case premature ejaculation is one form of sexual dysfunction, but that does not mean that there is total Erectile Dysfunction
In case of impotency there will not be any erection or minimal erection and a person will not be able to penetrate. In case of premature ejaculation there will be erection but coitus cannot prolong to certain extent that the person feels satisfied.
it is clear that the behavior of a person with impotency may be on account of various circumstances like if he feels that the other partner is not co- operating he may show hostile reaction towards the partner or if he is trying to suppress information there can be a tendency to exaggerate problems of a partner trying to show that she could be the reason for his impotency.
This cannot be considered as cruelty even if she files a petition seeking divorce from you.
Having regard to the sanctity and importance of marriages in a community life, the Court would always consider whether the conduct of the counter-petitioner (you) is such that it has become intolerable for the petitioner(your wife) to suffer any longer and to live together is impossible, and then only the Court can find that there is cruelty on the part of the counter-petitioner. This is to be judged not from a solitary incident, but on an overall consideration of all relevant circumstances.
Therefore you may remain silent without initiating any action in this regard, if at all she files any case seeking divorce, you can challenge the same properly and legally as per provisions of law. As far as alimony is concerned, if she is employed and drawing a a handsome salary then she may not be eligible for alimony or even maintenance.