What am I doing wrong?

Hi there,

I have been working on the Quant section for a month now, and I see no improvement in score, AT ALL!
I am really not a quant person myself (have a master in finance though, so stats/ percentage, interest calculus were fine but haven't done algebra or geometry for years).

I have read all the quant books from Manhattan GMAT, done the exercises, and finished the OG Quant. On the OG I see a real improvement and I have consistently scoring above 70-80%.

Nevertheless, I have done several MGMAT CATs, with always the same score: 38 (too bad, that could have been 48 )
If I am tired--> 38
If I am very focused---> 38
Bad timing--->38
Perfect timing---> 38

I must say I really don't understand why is my score not improving, as I can see myself a real difference when doing the OG exercises.
Happy to hear about your suggestions!