hi AnnH,
I've just taken GMAT as well, got 580 Q47 V23. This was my second attempt as well from my last 610 Q47 V27. I was really down as well after learning that my socore went down after 2 month of intense prep in Verbal.
My advice for math is work with OG10 and focus specifically in the last 100 questions of both PS and DS sections. They are harder than the earlier ones. Same goes to OG11. I also found the math questions in Diagnostic test of OG11 quite good. Don't need to go for Kaplan math books.
OG has well over 300 problems in each math sections and are quite representative.
I have the Manhattan math guide for Word Translation problems. This book is a good buy, since it also include probability, sets and stats. I wasn't sure about this guide in the begining, but after I read so many positive reviews in this fourm I was convinced. It is indeed a good guide.
Also, do you know which areas are you weak in? For me, after I did questions I found inequalities and absolute value problems are tricky. Then I just focused on those, and do other types of math problems once in a while.
How do you prepare for verbal? I've done hundreds of verbal questions and yet seeing any improvements
my story is also in
https://www.gmatclub.com/phpbb/viewtopic.php?t=24769