A three-inch erect penis is certainly long enough for you to have satisfactory intercourse, ejaculate and succeed in making your partner pregnant, assuming that you are heterosexual. It is also of sufficient size to achieve satisfactory clitoral stimulation for your partner. But I don’t think that is the point in your question. Although everything I have said to you is true you just don’t see it that way. As I see it you are standing at a crossroad, one path leads to physical treatments to increase the size of your penis and the other leads to counselling and attempting to alter your perception about the significance of its size. There is a myriad of bogus treatments available, including pumps and exercises, which I would caution against. You could arrange to see a surgeon who specialises in enlargement of the penis who could discuss with you the pros and cons of such surgery. Alternatively you could discuss your concerns with a sex therapist. My instinct is to recommend the latter course of action as your best first option. Most doctors would tend to be conservative about surgical modification of the body in the absence of pre-operative psychological assessment. I don’t wish to be insensitive or unhelpful but maybe the size of your penis is not the full diagnosis here.