Secret habit? How to expiate the sin? HELP

No problem! Allah azza wajal says Don't Despair!

The best thing to do is seek the Forgiveness of Allah azza wajal -

Tawbah means to turn oneself to Allah and to attempt to stay as straight as possible on the path of Allah's guidance, it is a lot more difficult than asking for forgiveness (istighfaar), however it is obviously the most successful and honourable path.Simply continuing in the crime and continually seeking forgiveness is a bit pathetic even though it is a weak human trait more fitting the one who is overcome and feels helpless, but since Allah is usually more patient than a human employer, there is sometimes hope of getting another chance to rectify mistakes.Let's try to fix our faults one by one.let's also bear in mind that lying is a root to sins, since giving oneself excuses and cheating other people of information they have a right to hardens the heart and turns it from weak to criminal, so it's important to answer valid questions truthfully so as not to add another black spot to the conundrum from which either more regret - and/or the need to fix that problem rears it's head too, and lying can be a festering cover for huge crimes which often tend to increase with each instance of unjust lying and falsely assuming that salvation has been achieved through unjust lies. It is therefore important to not go around bragging about one's sins, nor to unjustly lie so as to hide them thereby causing undue confusion, miscalculation, and enmity, whilst losing one's own weight of credibility.Lying also opens the door to being blackmailed since the liar's fate is placed in the hands of witnesses - of whom some may be very crooked and corrupt.Our father Adam wasn't perfect, but he admitted his fault and tried to walk according to Allah's good advice despite his lack of resolve, whereas iblees rejected Allah's wisdom and requested that Allah absolve him from his duties so that he could prove Allah wrong about humans whilst getting spiteful vengeance.Your attempt to seek the face of Allah after acknowledging your faults is an indication that you're not a rotten lost cause, but rather a child of Adam trying to walk in the right direction.A solution to problems - leave excuses only for the pathetic who will be asked: was not Allah's earth expansive enough for you so that you could have migrated?قَالَ رَبِّ إِنِّى وَهَنَ الْعَظْمُ مِنِّى وَاشْتَعَلَ الرَّأْسُ شَيْبًا وَلَمْ أَكُنۢ بِدُعَآئِكَ رَبِّ شَقِيًّا"He said, My Lord, indeed my bones have weakened, and my head has filled with white, and never have I been in my supplication to You, my Lord, wretched/miserable/hopeless/doubtful."Allah SWT said:وَإِنِّى خِفْتُ الْمَوٰلِىَ مِنْ وَرَآءِى وَكَانَتِ امْرَأَتِى عَاقِرًا فَهَبْ لِى مِنْ لَّدُنْكَ وَلِيًّا"And indeed, I fear the successors after me, and my wife has been barren, so give me from Yourself an heir" (QS. Maryam 19: Verses 4-5)