Is it obligatory to go to a doctor to treat sexual problems, despite the recurring nightmares after performing Istikhara, or should one rely on Allah and get married, considering the fear of incurring the wrath of Allah and one's wife if the estimations of sexual ailments prove true, especially after a previous experience of losing projects when going against Istikhara?

Complete or near-complete impotence is one of the defects that a man must inform a woman about before marriage, and concealing it justifies the annulment of the marriage. As for weakness that does not prevent intercourse, it is not considered a defect that necessitates annulment, nor is it obligatory to disclose it, though it is certainly better to disclose it to avoid disputes. A Muslim should visit a specialized doctor to diagnose and treat his condition. Dreams and nightmares have no connection to istikhara.