I am a 38 year old female. I think much of the problem men have is that they focus too much on the actual sex and not on love.For example men start talking about positions etc. If the actual sexual act of having sex is the main focus then that it when things will get boring.INstead of being romantic it will be cheap and tacky and a turn-off. YOu should not get bored of making love(I do not mention the word sex)to someone you love.
I hpoe I do not sound sexist.YOu do not sound like this which is why you are so concerned with doing it right. For girls a display of affection is what makes it work, therefor the forplay is very important.
When you know her a little better and you have each others trust and confidence then you can relax more and things will just happen.You will realise you had nothing to worry about.