How long have you been on the higher dose? Could it be that your body is still adjusting to it? When I was increased from 50 to 75 recently I was feeling like a total space cadet for about 2 months with dizziness and feeling weird. I'd talk to your GP if you're concerned about it.
Archie: The palpitations I get when I'm a bit hypo feel like my heart is beating harder than normal, I'm suddenly aware of it beating. After 5 or 10 or so it seems to do a little flutter, like 2 halfbeats really fast and then it goes back to normal... Really freaked me out until I worked out what was causing it - changed to a brand that didn't seem to work as well for me so I was going hypo. fun