Hi Chamber66, I am a retired chiropractor, so I may be able to offer some advice for you to check out where you live, to see if there is help available.
I say check it out because things are different in different countries. What country are you in
First good you have had the MRI makes the diagnosis correct.
I'm thinking from your problem that is a disc bulge at L5 and maybe L4 a little less.
Your yoga was a great solution until it blew up as it makes the core strength in the muscles that support the spine carry the load.
When the degeneration/injury causes the bulge to put pressure on the nerve well there is sciatica.
First course relieve the swelling of the bulge and injury and the surrounding tissue that increases the pressure on the nerve.
It also seems that you have been developing this problem over a few years, most people know if they do it as a one time acute injury.
If your body and your medico find it fits your current health profile some pain killers ( doesn't fix but relieves pain) and or some anti inflammatories, ( again doesn't fix but decreases swelling) Usually both are prescription drugs, follow instructions.
Postural relief, you can lie on the floor on your back hips to knee upright at right angle from body, knee to ankle at right angle resting on chair lie there for a while this can allow the disc and tissue to lessen their swelling.
Other relief, get safely into a swimming pool and just walk while de-weighted, don't swim.
Some massage may relieve it slightly but it also can cause more problems, you need to have masseur you really trust.
Again massage is only a relief technique at this stage, better value later.
Physiotherapy (this my opinion) is great for rehabilitation after muscle and limb injury but I find the spinal manipulations that Physio's use in Australia not as beneficial as they could be.
Chiropractors do manipulations that may help but all in all the discs are degenerated so other than taking the mechanical misalignment pressure off the disc and inflammation/swelling will decrease but the underlying problem is still there.
If you can get the spine structurally aligned the stress on the disc will be as little as it can be, then build a musculature that supports the spine this is after you get past the acute stage pain etc, you are well cautioned to consider lifting and weight carrying techniques as a start.
Next I would resume Yoga and/ or take on Pilates making sure that your teachers know of the back problem.
All this is particularly important if you have a sedentary job.
My suggestion for any surfer is to have a team of a Medico, Chiropractor , masseur and physiotherapist hopefully all of whom surf or at least understand surfing and are prepared to talk and work with each other.Just a general note here, this is general advice
I haven't examined you so it is based on how I would treat a similar case here.
That fact that you had an MRI helped, for others reading this post, not all back pain has the same cause , get diagnosed properly by a professional a
nd then you will have a clear path to follow to recovery.
I've taken up troll hunting just for fun, instead of a rifle I'll just use a pun!