>I want to start learning stuff again from square one
Where is square one? What scientific subjects interest you?
The Extended Phenotype is a good book on evolution.
The Grand Design is a good book on physics and the universe.
Consciousness Explained is a bit challenging yet interesting look into, well, consciousness.
How far do you want to go though? Perhaps you should learn first-order logic (start with simpler logic first), improve your maths skills on Khan Academy, get a book on statistics (which will help you read scientific papers).
It's a bit hard to help when you're being this general.