Warfarin increase, INR decrease - Please help!

Hello,

     My name is Molly. I've been taking anticoagulants for a little over a year, now.  I had five pulmonary embolisms and one clot in my knee.  I have a low Antithrombin III level and a high Fibronigen level.  My PT-INR dropped from 3.0 to 1.7.  My doctor increased my dose, to 7.5 everyday, instead of five of the seven days, where I'd take five miligrams on two fo the days.  After two weeks of taking 7.5 everyday, it dropped, again, to 1.4.  I was wondering, why would my Pro-Time keep dropping, when they're increasing my dosage of Warfarin?  Please get back to me, as soon as possible, thank you.

Sincerely,
Molly Von Rhin