I am sorry to hear about your ongoing challenges: as you know, I can not give you any medical advise as I am neither a doctor nor a physiotherapist, but I can offer you some perspectives. First - have you ever noticed the care that an airplane pilot takes before he even begins to taxi his plane to the runway? There is a complete checklist that covers all the possible ways something could go wrong. Compare this to the degree of care that our doctors take when we visit them: there is no checklist. Every doctor has her own way to help a patient. Often our time with our doctor is limited and we feel rushed - they have to get to the next patient. This doesn't mean that our doctor doesn't care, or isn't qualified: I believe all doctors do care, but the big difference is - the pilot is on the plane with you! Your doctor, no matter how caring she is, is not living your life. You are the only one on your plane. You have to be your own doctor and treat everyone else as part of your consulting team. If one consultant does not give you the advice you need, find another one. Don't accept results that are unacceptable: keep working to find a solution that works for you.
Being our own doctor is not easy: doctors are well trained, but they have to be trained in everything, you only need to find what works for your specific current ailment. I would suggest you find another physiotherapist who has experience with possible tears in ligaments or muscles in the sacral area. I would also suggest you try other healing modalities. Doctors are trained in one particular paradigm, and Western medicine is incredibly valuable, but it is not perfect. You may find relief by seeing an acupuncturist or by working with a Rolfer. An experienced Rolfer can watch the way you move and notice where trigger points are, where your fascia may be restricted, how certain habitual movement patterns may be causing seemingly unrelated problems.
Next: if you do have a bulging disk, then forward folds and deep twists could make this problem worse. When we flex the spine forward, we compress the front of the disk, which pushes the liquid in the core of the disk to the back side, which can create the bulging bubble. Ironically, backbends such as Sphinx can help fix this, but for you Sphinx doesn't work. You mention pain when you brush your teeth in the morning: it is in the morning that our disks are the stiffest and leaning over the counter puts your lower back into flexion. Perhaps you can try bending your knees while you brush your teeth can add a little uddiyana bandha to support the lower back. You can still do Yin Yoga, but try to do the flexion poses keeping the spine straight. You may want to work to strengthen the lower back area: if you have the time, money and inclination, a good book to help you understand how to safely work the lower back is called Lower Back Disorders by Professor Stuart McGill. I refer to it in one of the Newsletters
Finally, the fear you mention is quite normal, but you do not need to feed it or act on it. This is a time to practice mindful awareness. It may be helpful to review the chapter in YinSights that describes the process of AWAKEN. You can see it here
. Accept that right now in your life, this is a challenging time: accept it but take appropriate action to resolve it if you can. Try heat, try ice, try other modalities. There is a chance that you have chronic inflammation in this area: if so, you may find the practice of earthing will help reduce the discomfort. I discuss earthing in this Newsletter
. You can order straps from earthing.com that may help your sacrum: just put the strap around the hips.
Good luck in your investigation - I am sure you will find your way to wellness with the right dedication and determination.