before practicing, try the book Yoga as Medicine by Timothy McCall.
There is a whole section on yoga for back pain and the appropriate precautions you should take. as well as recommended special pose modifications.
I dont believe there is a tape specificially for back pain. Depending on your experience level: Yoga for Inflexible People, is good.
you just want to be knowledgeable about what yoga can do to improve your pain, and what is dangerous. thats why I really recommend reading that book. The section on depression and anxiety was very helpful for me too.
There are several DVDs out there that specifically target your back. My experience is that you need to be very, very cautious in your approach when practicing yoga for back pain. It can be immensely helpful, but when pushed too far, too soon, it can aggravate the back.
I think the best ones out there (I haven’t seen them all, but you can do a search on amazon on ‘yoga back dvd’ to get an extensive list) are likely to be the Viniyoga Therapy series: Viniyoga Therapy for the Low Back, Sacrum and Hips and Viniyoga Therapy for the Upper Back, Neck and Shoulders. They haven’t been out long, but the exercises Gary Kraftsow uses in these DVDs have been used in studies on back care and came out as winners.
You say your stress and tension causes your back pain, it is likely it is also contributing to your weight problems. See articles like this http://aje.oxfordjournals.org/cgi/content/abstract/165/7/828 that support that theory. Finding some stress relief yoga tapes may be a good idea too, there are several short ones out there (try a search on amazon with ‘yoga dvd stress’).
However, if you want to do more of a workout type yoga to help with the weightloss (besides the stress relief), doing a short DVD isn’t going to do it. You’ll need to build up to more than 40 minutes of moderate exertion per a session to get fat burn going in your body. For weight loss I recommend combining stress relief yoga (especially in the evening) and strength-and-stamina yoga.
I would do the back therapy ones for a while first, though, until your back feels stronger and you have a good feel on what poses work for you and how to modify poses that don’t. Then add stress-relief and then move on to more physically demanding yoga.
Good luck on your journey!