Is a person considered a hypocrite if he committed major sins in the past and repented from them, but sometimes weakens before desires in private, and feels remorse and hardness of heart, along with his fear that Allah will not forgive his sins, and his remembrance of the Hadith: "those who, when they are alone with the unlawful things of Allah, they transgress them"?

You are not a hypocrite as long as your good deeds please you and your bad deeds displease you. Rather, you are among those who "mixed a righteous deed with another evil one." Regret is repentance, and "the one who repents from a sin is like one who committed no sin." Have a good opinion of Allah, for Allah accepts repentance and wipes away sins. Repentance from a sin is valid even if you persist in another. Whenever you fall into sin, hasten to repentance and seek forgiveness, and do not despair of repeating repentance. Increase good deeds that expiate sins, stay away from the causes of sin, and adhere to the remembrance of Allah and supplicating Him.