All my life all I wanted was to go to heaven. I was always happy with everything I had until one day I don't know what happened I wanted more and since then nothing seems to be going right. How do I gain that belief again?

Praise be to Allah, the Lord of the Worlds; and blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.

One of the trials for a person is that the life in this world could deceive him, by beautifying to him what is bad and driving him away from doing what is good. This life can cover some people with pleasures blinding them from the truth and making them feel very comfortable with wrong deeds and forget about The Day of Judgement. In fact, this life is nothing compared with the pleasures of Paradise on The Last Day. Al Tirmizi narrated that the Prophet said: "If Duniya (This Life) had the weight of the ala (wing) of an insect for Allah, He would not have quenched the thirst of any disbeliever from it (by giving him a drink of water)".
Jabir Ibn Abdullah narrated: Allah's Apostle (peace be upon him) happened to walk through the bazar coming from the side of Aliyah and the people were on both of his sides. There he found a dead goat kid with very short ears. He took hold of his ear and said: Who amongst you would like to have this for a Dirham? They said: We do not like to have it even for less than that as it is of no use to us. He said: Do you wish to have it (free of any cost)? They said: By Allah, even if it were alive (we would not have liked to possess that), for there is defect in it as its ear is very short, now it is dead also. Thereupon Allah's Apostle (peace be upon him) said: By Allah, this world is more insignificant in the eye of Allah as it (this dead lamb) is in your eye". [Reported by Imam Muslim]
The soul of the person is sometimes high (searching the good) other times low (inclined to the bad). So, sometimes the person feels a great pleasure in worshipping Allah and dealing well with all that is around him. Other times, this feeling gets lower. This is actually human nature. The person can not live on the same plain all the time. Abdullah Ibn Umar narrated that the Prophet said: "Each work has a vivacity and each vivacity has a period. So, if this person's period is spent in following my Sunnah he has followed the right path. But if his period is spent in something else indeed he has perished". [Al Bayhaqi]
We ask Allah to guide us and you to the right path and make our work sincere to Him and accept it from us.
Allah knows best.