Answer
Wa `alaykum as-Salamu wa Rahmatullahi wa Barakatuh.
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
In this fatwa:
In spite of all what you have said, you still have a chance. You just need to turn sincerely to Allah Almighty seeking His forgiveness and imploring Him to forgive you and guide you to the Right Path. Also, try to do as many good deeds as you can; these are the most deeds that expiate for bad deeds and draw a person closer to His Creator.
Responding to your question, Dr. Muhammad Salama, PhD, Islamic Studies in English, Associate Professor at the Faculty of Islamic Sciences al-Madinah International University (Mediu), states:
Out of His grace, Allah, the All-Merciful, has opened the gate of repentance wide for all those who repent sincerely and earnestly to Him no matter how grave their sins are.
In the Qur’an we read:
“Say, [O Prophet]: O My servants! Those [of you] who have committed [sins in great] excess against their own souls, never despond of the mercy of God! For, indeed, God forgives sins, one and all. Indeed, it is He [alone] who is the All-Forgiving, the Mercy-Giving.” (Az-Zumar 39:53)
The Qur’an also tells of the acceptance of sincere repentance from apostates:
“How shall God guide a people who have disbelieved after [they have professed] their faith and borne witness that the Messenger is true, and [after] the clear proofs [of God] have come to them? For God does not guide the wrongdoing people [who are godless in heart].
As for [the likes of] these, their recompense is that upon them is the curse of God, and [of] the angels and [of] humanity all together……. except for those [of them] who repent after this [breach of faith], and set things aright. For, indeed, God is all-forgiving, mercy-giving.” (Aal `Imran 3:86-89)
As for the verse 137 which you referred to in Surat An-Nisa’ which reads: “As to those who have believed, then disbelieved, then believed, then disbelieved, then [stubbornly] increased in unbelief- never will God forgive them. Nor will He guide them to [the right] way.” (An-Nisaa’4:137), it obviously speaks about those who adopt disbelief as the last choice in their life and die while disbelieving.
So, you really need to think seriously about it. You still have the chance. If you have any doubt or question about the religion, speak to scholars to answer your questions and dispel your doubts.
Turn honestly and humbly to Allah Almighty and ask Him to guide you to the truth and to enhance your faith. Recite the Qur’an frequently and regularly and establish the daily prayers. Look for religious friends (these are found mostly in mosques) to be with you and support you.
Allah Almighty knows best.