Welcome to HCM,
Size of penis is genetically build up so nothing can increase the size.
Nothing to worry 3-4 inches size of penis while erected is enough to satisfy your partner.
You mean to say that ejaculation is very soon,nothing to worry,you may prolong ejaculation by diverting your mind during sex.
You may take tab. Viagra
after consulting your doctor for ejaculation problem.
Ok and bye.