I had been feeling restless, anxious with constant worry and thoughts. I cannot find happiness or satisfaction. I had taken professional help and I am on medication from three years but there is no cure nor do I feel better. I am always concerned about my health, my future and my past sins. I am not offering Namaz and I do not know why is this happening, I need your help.Please suggest a course so that I resolve the issues and feel happy without being worried.

Firstly, may Allah alleviate your pain. You need to understand that happiness and satisfaction is only a result of being content.
Medicine is only a placebo when it comes to these issues.

Despair is the bane of hope, it is the opposite of hope, it is a distinctive feature of the unbeliever.
Allah says in his Holy Quran

إِنَّهُ لاَ يَيْأَسُ مِن رَّوْحِ اللّهِ إِلاَّ الْقَوْمُ الْكَافِرُونَ
[12:87] surely none despairs of Allah's mercy except the unbelieving people.

There is a deep rooted connection between despair and disbelief. Because the disbeliever’s thoughts and beliefs are all based upon cause and effect; They don’t believe in الإرادة الإلاهية (Gods will or wish).

The physical laws pertain to us, he transcends all of this.

The nature of this life is to have problems and issues. We always hear people complain about their issues, but we are here to be tried and not to live in comfort, comfort was only created for the hereafter.

An individual upon encountering a problem automatically feels it is the end of the road.

إِن مَّسَّهُ الشَّرُّ فَيَئُوسٌ قَنُوطٌ
[41:49] if evil touches him, he is hopeless and despairing.

The believer in the worst situations should fill their heart with hope.

Things always change, don’t forget that God fixes things.

Remember when you were young and how you never worried about anything because your parents had all bases covered. Why do we lose this as we grow? When Allah is far greater than our parents at looking after our future and resolving our issues.

You need to remember
1. We were created to be tried
2. This world is transient
3. Allah rewards us based on our resolve in these situations.
4. Only the first hundred years are difficult for the believer. After that is eternal enjoyment.