Does repeatedly watching pornography and stimulating lust, leading to ejaculation, affect one's future? Is this considered masturbation? And can this sin be forgiven after repeated repentance?

You must hasten to repent to Allah, the Almighty and All-Glorious, by regretting your sins, seeking forgiveness, abandoning the wrongdoing, and resolving never to return to it. Committing a sin again after repenting does not prevent the acceptance of repentance once more. Seek Allah's help in repenting, follow up a bad deed with a good one and obedience, preserve your obligatory duties, be mindful of the harm of sins, associate with righteous companions, and turn to the Book of Allah. As for the effect of watching pornography on health, that is a matter for specialists. Let the motive for repentance be seeking Allah's pleasure, not fear of these effects.