You are right, I don't know if my place is in Heaven or Hell as it is for Allah to judge and even now my heart trembles from the fear of Allah's wrath. Oh, to be so assured of salvation as the Christian claims!You don’t know if your saved, but I know that I am.
Quran 2:111-112 They say: "None shall enter paradise except he who is a Jew or a Christian." These are their vain desires. Say O Muhammad: "Let us have your proof if you are right in your claim." Yea! Whoever submits himself entirely to Allah and is good to others will be rewarded by his Rabb; he will have nothing to fear or to regret.
From the Muslim perspective the unforgivable sin is "shirk" which according to Alim software definition is "associating partners with Allah. Shirk can also encompase any object that a person may hold in regard higher than Allah. It is the most severe of sins and will not be forgiven."
Quran 4:116 Surely Allah will never forgive the one who commits the sin of shirk and may forgive anyone else if He so pleases. One who commits shirk has indeed gone far away from the Right Way.
We believe to say that Jesus (pbuh) is the Son of God and at the same time God is commiting shirk because it is deifying Jesus, a human born of the virgin Maryam.
I have the promise of Allah for Paradise and pray that I am a true believer and not a hypocrite. He knows my heart better than I do and only He knows my state of faith when I will die.
Quran 4:124-125 But the one who do righteous deeds, whether a male or a female - provided he or she is a believer - shall enter paradise and will not be harmed a speck. Who has a better Deen (way of life or religion) than the one who is a Muslim (submits himself entirely) to Allah, does good to others and follows the faith of Ibrahim the upright one, whom Allah chose to be His friend?
I stand on this oft repeated promise in the Quran and pray for the forgiveness of Allah. May Allah guide you to the Straight Path - siratal-mustaqueem. Peace.