I tired having sex with my partner in the bedroom today but couldnt get hard at first i felt it getting hard but then it didnt want to anymore after a small pause is it libido? low t? or ed. but at home i can watch porn after hard and able tofinish?

No problem with libido, not enough stimulation I guess. If you have sex so often with the same partner, your body may behave that way too even you are still young.

You may be having relationship problems because if you are physically healthy so much of sexual arousal is psychological. Please see a Clinical Psychologist with expertise in multiple types of psychotherapy to help you.