"Am I responsible for my previous actions after I start to live by Islam?"
According to the Qur'an, people who do not know about Islam are "ignorant" and cannot distinguish between what is right and what is wrong. Once they embrace Islam, however, they obtain this knowledge, leave their former un-Islamic ways behind, ask for Allah's forgiveness, and repent. As a manifestation of Allah's infinite mercy, He promises to accept all people's repentance and transform their wrong actions into good, provided that they sincerely turn to Him, repent for their sins, and follow the righteous path:
Repentance is an act of worship that is not unique to new Muslims. In reality, it is a lifetime worship performed by all Muslims, one that guides them to Allah's infinite mercy and forgiveness, for no believer is immune to committing sins and making mistakes.
In Allah's presence, believers strive to maintain a balance between hope and fear. Given that they cannot know their situation until they die and face Allah on the Day of Judgment, there is no way for them to feel secure against Allah's punishment. This aside, no matter how desperate their situation or how great their sin, they do not despair of Allah's mercy.
One of satan's greatest tricks is to infect people with hopelessness by causing them to believe such things as: "It is too late," "No one can save you now," or "You have already immersed yourself in sin." By insinuating such false claims, satan and his followers seek to distance people from Allah's mercy. Allah warns people against this trap in many verses and calls them to ask for repentance and forgiveness:
Seeing these verses, those who have true faith in the Qur'an can escape the trap of hopelessness.
However, those who insist upon their sins and continue to disobey Allah's commands and prohibitions on the grounds that "Allah forgives in any case" fall into another trap of satan. As long as they do not regret what they have done and turn to the right path, their repentance will have no worth, for Allah makes clear in the following verse what type of repentance He accepts:
To conclude, those who forsake their former actions and resolutely turn toward Islam are not held responsible for what they did in the past, no matter how sinful their activities were. This assessment also holds true for believers. In other words, believers pay no attention to what people might have done before embracing Islam, for from then on, the Qur'an will regulate their days and they will be held responsible for this in Allah's sight.