Suzy,
I'm sorry to hear of your experience while looking at Venus.
Fortunately, I've never had any eye troubles when looking at Venus. I would think the amount of light you'd get in your eye would be the same regardless of the eyepiece focal length. Certainly the aperture would make a difference but I've looked at it through my 8" newt with no problems.
If you're worried that you've done some damage a visit to your local optometrist might give you piece of mind. Don't give up on Venus, the phases are wonderful!
Mario