I have been on Warfarin for 12 years and I am only 18 years of ag...

I have been on Warfarin for 12 years and I am only 18 years of age. I was born with a congenital heart defect and have had many operations in the first 6 years of my life, including 3 open heart surgeries. When I was 6 years old I had my last open heart surgery where they put in a St Judes mechanical valve. I don't know what my dosage was when I first starting taking Warfarin, but I am now on 7.5mg with an INR between 3.2-3.5 Sometimes I feel like I have a little bit of memory loss. I would forget the most basic words.. but I'd slightly remember what it looks like. I'd have to sit and think for a while until it would pop into my mind again. I really do hope that I don't get other side effects such as hair loss :(