All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
First of all, you must know that it is forbidden to watch pornographic movies. Therefore, you have to repent to Allah for having watched them in the past. The conditions of repentance are highlighted in Fatwa 86527, so please refer to it.
If you had informed your parents about the sin that you had committed, then you were wrong, because it is an obligation on a Muslim to conceal his sin and not inform anyone about it.
Abu Hurayrah said: "I heard the Prophet saying: ‘All my nation will be forgiven (for their sins) except those who sin openly (disclose their sins to others). An example of such disclosure is that a person commits a sin at night and, though Allah covered it from the people, he comes in the morning, and says, ‘O so-and-so, I did such-and-such (evil) deed last night’. During the night, his Lord had covered up it (the sin) but in the morning he removes from himself the cover with which Allah covered him." [Al-Bukhaari and Muslim]
We do not know of any religious evidence proving that a curse befalls someone if he breaks this type of a promise.
Allah knows best.