Hi Waltztime
I may not be the best person to answer this, as i'm a man, but i've had a lot of problems with my frame and posture because i played tennis for decades, and if you look at the posture of tennis players, you will know what i mean.
Is your problem only stiffness? First, you almost certainly aren't stiff at all, it's just the you don't know waht to do. since you've been dancing only 6 months, that's normal. It'll take you a long time (many years, i'm afraid) to get a really good frame.
What works for me is the following:
Pick a very short segment of relatively basic steps (say, natural turn, link step, reverse turn in slow waltz)and concentrate on dancing these steps very well, with correct body shape and alignment with your partner. Get your coach or teacher to help you with this. This will tell you WHAT to do, and if you practise sensibly, you'll get used to HOW to do it. Eventually, it will become natural, and you can relax into it, as it were.
I found that even when i relaxed, i didn't know what to do, so still looked very stiff.
Your partner has a part to play too. He mustn't hold you in a vice-like grip. Only a teacher can sort out your hold as a couple.
But don't worry too much. Get the basics of foot- and leg-work, timing, movement, posture and working with your partner correct. That's enough to be going on with. Everything else will follow
