Praise be to Allah, and peace and blessings be upon the Messenger of Allah. To proceed:
Faith (Iman) increases through obedience to Allah and decreases through sin. What you are experiencing is something many believers go through. The important thing is to strengthen your relationship with Allah and not surrender to periods of spiritual weakness.
Among the greatest means of increasing faith are:
Allah, the Exalted, says:
"Indeed, in the remembrance of Allah do hearts find tranquility."
He also says:
"The believers are only those whose hearts tremble when Allah is mentioned, and when His verses are recited to them, it increases them in faith, and upon their Lord they rely."
Do not think that your acts of worship are insignificant or without value. The deeds most beloved to Allah are those done sincerely for His sake and performed consistently, even if they are small. What matters is that your heart remains attached to Allah, striving to obey Him, hoping for His mercy, and fearing falling short.
Whoever wishes to increase their faith should recite the Qur'an frequently, remember Allah often, maintain the obligatory acts of worship, strive in voluntary acts of worship, keep the company of the righteous, avoid the causes of heedlessness, and frequently ask Allah for steadfastness. Hearts are between two Fingers of the Most Merciful, and He turns them as He wills.
And Allah knows best.