Hi Ankchy,
If your neck is very bad, you may have to go back to your osteopath or a chiropractor. Maybe you have financial concerns that prevent it. You might only be able to do the poses Victor suggested. You won't get much inversion effect from them but you will get some. Maybe it is just what you need. You be the judge.
The first pose I mention is a personal favorite of mine as there is hardly any stress on the neck and you still get the inversion effect altho not as good as with shoulderstand. It is in fact, viparita karani light as the only difference is that the knees are resting easily on your forehead. (the picture of the pose in Yogani's asana book is one version of viparita karani; another is with the legs hanging over head at a 45 degree angle). The hips are not directly over head so there is not so much stress on the neck. I use it prior to plow and shoulderstand and stay in it until my body feels ready for more. But you can just stay in it and go no further.
You know, you can feel your body wanting that stretch you get in the plow and that pressure in your head and neck you get from both plow and especially shoulderstand. You just can't get it any other way. It feels great after a long day at work. Well, sometimes you just have to sit on the side lines.
I had a bad car accident back in '91. So I have to pay attention to my neck like you and be careful not to over do. But I can still do plow and shoulderstand. Sometimes I have to back off a little. If I have a problem with neck pain, I get my spine adjusted and things are fine again. It is permanent injury. Can't be fixed but can be managed.
I have many people who come to me regularly for chiropractic care, like going to the dentist to get there teeth cleaned. Chronic joint symptoms are rampant in our society and chiropractic is often the best answer, especially if combined with some type of self help like yoga postures. It greatly improves the quality of life for them. So you might want to consider using that combination. You responded very well to what the osteopath did. So no reason it won't happen again.
Keep in mind that about half the people who are middle aged are walking around with herniated discs and have no pain from them. How do we know this? Because so many times a person would have an MRI for some other health concern and there would be a herniated disc or two present. They would ask the person if they were having any pain and the person would say no I am feeling fine.
So you may have some herniated discs but it could be some other part of your spine, like a facet joint, that is the symptom generator. Could be the discs, too. No matter. It is what happens in real life and what your body responds positively to that matters free of the limitations of some rigid model or belief system.
We chiropractors say there are 3 causes of subluxations (stuck bones) in the spine. The first is physical stress. That can be from a big injury or many small ones. The second is mental stress. The third is chemical stress.
Two things I think help immensely in this regard.
First, I think that an advanced meditator can have a great impact on their experience of physical pain and spinal function, even tho they may have some significant degenerative arthritis (joint inflammation), because there is far less emotional stress radiating thru their nerves into their muscles which then pull on the spinal bones and create spinal stress and tension.
The second is an anti inflammatory diet that minimizes inflammatory chemicals in your body that egg on any inflammation that is already present caused from physical stressors (it is physical injury that causes degenerative arthritis which is what chiropractors treat).
Maybe that will give you some more perspective on what you are dealing with. At least some food for thought.
The bottom line is use your common sense and stay within your comfortable capacity. Experiment. Find out what works. If it hurts, don't do it. Simple. Sounds like you are doing it.
BTW, welcome to the forum.
Best, yb.