Will Allah invalidate all or part of my deeds because of this sin of mine, and will Allah be angry with me or will His curse descend upon me even with seeking forgiveness and saying "Subhan Allah wa bihamdihi" (Glorified is Allah and with His praise) a hundred times? And am I committing a major sin?

It is not for a servant to abandon seeking forgiveness for repeatedly committing a sin. His good deeds and acts of obedience are not lost, and not every sin necessitates a curse. One must beware of the whispers of despairing from God's mercy. It is appropriate to feel that you are a sinner, not to declare it to people. There is no hypocrisy in hearing people praise you if you did not say anything. The best cure for obsessive whispers is to distract oneself from them and to supplicate to God.