Hello thanks for asking from HCM
You have a lot of misconceptions about psychosexual health. First of all, as you are also aware,
masturbation is not a bad thing and it is a safe and healthy practice.
Size of penis varies between individuals and there are a lot of factors that determine size. If you have good erections then size doesnt matters. The size of 4.5 inches in erected position is pretty good so no need to feel inferior while using public toilets. Don't loose your confidence you are absolutely normal.
Now coming to the problem of discharge while talking to girlfriend, the discharge is not ejaculate but it is the seminal fluid that is secreted by seminal vesicles and it is a lubricating fluid that helps in lubrication during sexual intercourse.
Ejaculation earlier than normal time is called a
premature ejaculation. If you are not reaching proper orgasm then
consult a psychiatrist for help. Medicines like SSRIs as
Dapoxetine when taken on SOS basis have excellent roles in premature ejaculation. Consult a psychiatrist for prescription.
Herbal medicines like Confido, Tantex Royal also have good effects.
Thanks, hope this helps you