Hi,
sorry to hear about your pain. It's hard to give specifc advice since I can't know exactly what your problem is. I've had back problems for +10 years so know a thing or two. You are best of researching the issue with or without the help of an osteopath (personally I would bypass doctors and use only for pain meds). However there are a number of low risks things that can be done which might benefit and certainly can't do any harm (if they cause big pain - STOP!).
It sounds like, from your bathing example, that part of the problem is caused or made worse by muscle tension. The body has reflex to tighten muscles to protect damaged areas, though with back problems this can a) make the pain worse and b) is a problem in itself. Look on google for 'stretches for bad backs' etc. Start with the most gentle and progress gently. Stop if the pain is screamingly bad or obviously doing damage but don't be so cautious that you do nothing. I mean, many people slip into the groove of dong nothing because it causes pain but if the pain is only very mild and temporary, like the pain from streching muscles it can be worthwhile pushing through it (this might sound crazy but it's my experience). Listen to your body but don't use moderate pain as an excuse to stop. Over cautious attitude is as bad as over-exertion in my experience. This advice comes with the big disclaimer I mentioned before, If you get massive pain or a huge adverse reaction then clearly stop. It's ofcourse best to the best diagnosis you can before doing anything and like I say you can use an osteopath for this - they will also tell you the best exercises.. However, unless the pain is massive I would be inclined to start yourself and save some money and time - it's unlkely you will make it worse, (if you are suitably gentle and ramp the duration sensibly). The exercise will also give you good information on what the problem might be and what works for you.
More generally it's likely that you will need to look at how your lifestyle is contributing to the issue and what you can do about it (sorry but this is true). It's probable you know what has caused the problem, either protracted sitting, heavy, repeated lifting or some combination (likely the former). The things you can do then are to reduce the factors that make it worse (less sitting, lifting etc) but more so make your body more resilient by improving your posture, core strength, flexibility etc. All the information is out there, there are no short cuts unfortunately though once you get into good habits it is easy and they will benefit you in other ways. Things like yoga, alexander technique are excellent life skills to have and well worth a try.
As an extra I'd like to share some advice regarding doctors and osteopaths. I know you didn't ask for this, but heh (skip if you want). You say you are frequent flyer at the doctors, so I thought I would add this. Personally I would avoid visiting doctors unless the pain is massive or you having very big restrictions. You have to understand that there is very little a doctor can actually do for you that you cannot do for yourself. All my doctors 'zone out' if they hear the words back pain. They are only 'good' for issuing pain meds and other pain mititgation methods (accupuncture etc) though pain meds should really be used in conjunction with management techniques and when other management techniques have failed. If you start using pain meds as a crutch or 'cure all' you are setting yourself up for bigger problems in the long run and probably be dissapointed. You have to remember also that surgery on backs is only of benefit in a tiny minority of cases (when all other avenues have been exhausted) so it's unlikely to be an option for you - since the risks of back surgery are so massive. Like I say, it all hinges on what kind of problem it is and as such the first step is to get a good diagnosis.
As for osteopaths, I would say from my long experience that they of limited benefit in the long run. If you can find a good one then they will be able to give you a good diagnosis and the stretches,exercises to help. What you have to remember that is that whilst not all are money suckers, they are not positively motivated to cure your problem AND most importantly there is little they can actually do they will have any lasting benefits. The truest thing I ever heard from an osteopath was ' What I do for you is irrelevant compared to what you do yourself '. It's like paying a plumber by the hour and being surprised when the problem is never fixed. Basically they are good for information, a good diagnosis and only if you:
a) have money to burn and
b) don't have the time, inclination or will power to stick to a exercise, stretching routine.
TL;DR - Research the issue, try some gentle stretches, consider lifestyle changes. Use an osteopath for diagnosis and establishing a routine and longterm if you need the help. Use doctors for pain meds and/or when the problem cannot be otherwise managed.
Hope this was helpful.
Andrew