There's a bajillion variables on road bikes. Sounds a bit like there's too much weight on your arms to me, but I dunno. I'd definitely recommend professional fit. I've never done it but I spent ages and lots of money on bars, saddles etc on my bike and finally got it pretty good. Then I was riding along in front of this old geezer the other day and he told me that my saddle was too high cos my pelvis was rocking from side to side. I had thought the height was spot on (based on the heel-straight-leg thing) but I lowered it anyway. Felt really weird at first but I've kept it there and it's really helped even more.

Another variable is the shape of the drop on your bars and the angle of rotation, and consequently the position of the levers. I fiddled with this for ages, now I've got it right at last. Previously I was almost unable to use the drops, now I can ride 80% of the time on them.

So what you think you know might not be right, hence professional fit.