In a one day I cum three times daily because I get relaxed but when I do sex my gf penis did not get big. When I see porn or think it get big??? .....

ED Issues. Not sure what your question is, but it appears you may have a type of Psychosomatic Erectile Dysfunction, which is fancy doctor talk for having difficulty getting erections from "Thinking about your sexual issues, and being fixated on Porn, etc." It is almost a type of "Stage fright" or Performance anxiety. You can seek the help from a sex therapist if your issues persist. Good luck.