Scribelady, good luck!
I too had sent over 200 queries and had a decent amount of requests, but most resulted in rejections - or fulls with no response after six or so months.
After my last re-write, I became depressed when I realised there was no one left to query! So, I went back to square one and chose a few agents I'd queried over a year ago, when the manuscript was an entirely different beast.
As it happens, these select few requested fulls and in around ten days, two - yes two!!! - of these lovely agents simultaneously emailed me to arrange phone calls! I was out of my head with excitement. Then, after I sent off some 'courtesy emails' to the others still with fulls, I received multiple offers! Yes. Multiple!
It's a cliche, but I was literally walking on air, with a huge smile on my face, for days. I still have that smile now, three weeks later, and cannot believe that I'm now agented - especially considering I'd almost given up.
Sorry, this post has turned into a bit of a 'How I got my agent' story, but, my point is this...
It's never too late and hang in there, because the right agent is out there somewhere... hopefully the one reading your full this minute