What is the reason for feeling constricted and religiously remiss despite performing daily prayers, supererogatory acts, and near-daily Quran recitation?

The questioner's feeling of inadequacy in turning to Allah and weakness in mindfulness is a good sign and an impetus for more obedience and mindfulness. The Companions complained of similar feelings to the Messenger of Allah, peace and blessings be upon him. This is a praiseworthy fear that motivates its possessor to perform many good deeds. However, this fear should not intensify to the point of despair.