I do not think you're being paranoid. I believe your concerns are valid. I have done yoga for several years and I am overweight with back and wrist issues. Yoga can be great for anyone even if you are overweight. The main thing is finding a teacher that is experienced and knowledgeable about modifications that you will need to make to do some of the positions. I would visit the studio and find some time to speak with the instructor. Let the instructor know what your concerns are, what your goals are and the general condition of your health. The answers will let you know if this is going to be an accepting and safe place for you to practice.
I believe that yoga is good for everyone but be sure to go into it with your eyes open. Just remember (and the instructor should emphasize this): Yoga should NEVER hurt. If you feel any pain during a position you must come out of it and modify it. You might feel sore after your first few sessions but you should not feel any pain during. Definitely try it out and see how you like it. It is very addicting.
