Is it possible to have zero interest/attraction in real sex with my girlfriend because watching too much porn for years?

Desensitization: YES: Give the porn a break and use it as a spice. Too much porncan cause desensitization. Don't forget, these are actors and semi-professional sexual workers, and you are not. Use alternative stimulation like massage, role playing, prolonged foreplay without intercourse,massage, aromatherapy, music, tantric meditation, oils and lubricants. The porn should only be used to "spice things up".

Yes, but...: The short answer is yes. The longer answer is that porn represents fantasy that is free of commitment or intimacy. In real life, most often, sex within relationship to another person requires some degree of commitment and intimacy. There are no rules or boundaries in the bedroom among consenting adults, so I would encourage you to share your concerns as well as your desires with your partner.