Hi Kawaii
You don't say whether you're male or female. Also, how 'comfortable' you are with your partner.
You must both be completely at ease with the body contact thing. Assuming that this isn't a factor then the first thing you must do is tackle the "butt out" problem! You will have to tilt your pelvis and practise holding this posture. Try standing against a wall and pressing the small of your back into the wall.
The only other thing i can suggest is that you move through some basic steps VERY slowly (obviously without music) as realistically as you can, concentrating on maintaining good contact. Try to get your legs as tangled (with your partner's legs) as you can! i know this sounds silly, but it's a good picture to have in your mind while you're trying to solve this problem.
Your coach should have some ideas too. It's hard to suggest a good solution without seeing you dancing

My back alawys hurts. I was born with it so it's hard for me.

Kawaiidancer. Bad back. Try Polates with a qualified instructor.

Don, I think you mean Pilates. And yes, check out the instructor's qualifications. It used to be that people certified in the Pilates method had to train for a year and then do an internship before they could be certified. Now one can be certified to teach a mat class in just six weeks. It's worth it to find the most experienced instructor you can, preferably one who is (or was) also a dancer. I love my Pilates teacher...she's been training people for over seven years, and is also a dancer (ballet, modern). She is very interested in ballroom and watches my competition tapes and even comes to watch my competitions so she can better understand what I am trying to accomplish and what I need to develop to get there. She's been a huge help!!

It is not possible to maintain contact and have vertical posture unless you do a perfect job of moving your body over your foot and not letting your foot move ahead of your body. Few dancers can do this - which is why at world championship level you see two different strategies: those who aren't all that concerned about losing contact a little bit, and those who are willing to dance with an arched back.

I would strongly suggest using perfect posture and not worrying about contact at all right now - you can add that later as your leg action improves to keep your body more over the moving foot.

I agree...work on perfecting how you move your body over your feet and on your own dance posture in general before you go for contact.

Anonymous. An arched back is now a major fault. Foreward Walk. If you take a look at the computor pictures on this site of a foreward walk you will see that the foot is ahead of the body, the knee also. This doesn't mean you pull yourself along with your leading foot. but use the back foot to push yourself onto the front. Take a look how a person walks up a hill. The foot and leg go first, then there is the push with the back foot, any other way and you are in big trouble. I think the young lady needs to look closely on how to set herself with her partner. If anyone cares to look at the set up of any couple in a major international final, you will see the man extends his right arm straight out in front. The lady walks in untill her left armpit is on the man's wrist. As the man bends his right elbow to a pre predetermined position. Lady places her hand into a comfortable position on the man's upper arm. Man keeps the lady on his wrist and bends his hand into a comfortable position, the hand is only a decoration. Lady goes well to the man's right side to fill up the available space. The longer the mans arm the further she goes. Right side will be to the right side. Contact point is just below the mans ribcage. Below that is a open space. Tango is entirely different.

Yes, the computer simluation of walking is very nice... now go look at the videos here of actual dancers demonstrating basics, and you will see both arched backs and thighs colliding with partner. Or look at any of the high-level Italian couples - arched backs. Apparently its gone from being a fault to being
"artisitc shape" - though the English are still holdouts for good posture by and large and as a result you will see bits of daylight in their winning performances.

Anonymous. How does the lady lean back over her heels and still, as you say not let the feet go first.

She abosolutely doesn't lean back over her heels! Ever!

That passage in the description of a walk is so commonly misunderstood, because it is poorly worded.

When she is just standing there, her weight is forward in her foot. If she goes to step backwards, she needs to move her weight back in the standing foot before she leaves it. But she does this not by leaning back, but rather by moving her entire body, hips and shoulders back, while preservering alignment.

The computer model, which has the wrong leg timing, does gets the weight/posture movement right. Some dancers lean back and cause problems that way. Wheras others attempt to use the leg timing shown in the computer model, causing their overly protruding front legs push their bodies apart - requiring arched posture or loss of contact. You can see that at various points in the demonstration figures here.