How can you rid your house of 'Sick Building Syndrome'?
Sorry there is no such thing as 'Sick Building Syndrome', it is just a lazy way to label a problem that is not understood.

So you first need to find out in detail what is causing the problem.

Given that your wife is expecting, it may have nothing to do with the building at all…..

A doctor may be able to do tests and give you a list of the things she is sensitive to, so you have somewhere to start – it could just be something as simple as dust you liberated while clearing the room to paint it and nothing to do with the paint.