I have had many homosexual patients. To my surprise, two of them turned out to be heterosexual after therapy. I do not know if psychotherapy would work for you, but you can try. Even if it does not change your sexual direction, it will be useful for you.
It is common that young men worry about their penises. But in reality, the shape of the penis very seldom matters. If somebody loves a person, they will love that person's whole body, even if it is not perfect.
Coming too quickly can be cured with medicine and various techniques. A psychiatrist will know about drugs; a sexologist or a sex therapist about other ways of handling this.