'Sounds to me like your body is telling what you need to do 'loud & clear', eh?
When it comes to "cleansing protocols", listening to your own doctor within is FAR superior to any guidelines, protocols, or 'instruction sheets'. This is always the case ASSUMING you know what you're listening for and how to interpret it.
In the case of water/juice fasting, you'll find it VERY common that flushing is recommended. Without oils, the bile flow through the liver is substantially lessened. There's two different schools of thought (maybe three) on this...but it's said that the liver creates stones & debris and the body is cleansing itself (via the fasting), or the liver dumps what it already has in it as part of the cleansing (via the fasting).
Either way, it's common to end up with a pregnant gallbladder that desperately wants cleansed.
And yes, what you report sounds like a gallbladder attack. I recommend flushing asap ( you may have to flush a couple of times in a few days once the gallbladder is in a state of distress). One or two Liver Flushes
is NOT going to ruin your plans (nor is it going to undo all the good work you've been doing! :) You are assisting your body to cleanse and restore itself; IT is assisting you by telling you (via pain & symptoms) what it NEEDS you to do. That's part of the healing & restoration process - and the more you listen to your body, the faster you'll progress. It's when we get hung up on 'instruction sheets' and 'book learning' that we usually end up in trouble.
If you absolutely don't want to ingest the oil for a flush, you could take a dose or two of Epsom Salts
(about 2-3 hours apart) and do a coffee enema
(as soon as the butt-pee passes after the last dose of ES). I have known folks in gallbladder distress to actually pass stones just from the Epsom Salts
...and then even more with the coffee enema. You can assist this process to be even more effective by ingesting fresh ginger root juice or fresh garlic juice (or just a clove of garlic/piece of ginger, or a tea/decoction made from the same -brewed STRONG). Both are cholegogues/cholertics and assist the liver to create bile.
If it were me I were "hard core determined" to finish the fast without ingesting oil, I would go the ES/ coffee enema
route first, to see if I could get enough relief to finish the fast. But if I didn't get immediate long-lasting relief, I would flush (and then flush again in a day or two if I still had ANY pain/tenderness...or follow the flush with several coffee enemas
over the next few days). BUT, I've been flushing and putting coffee up-me-bum for years now, so I'm very comfortable with what I do (and I can hear my body VERY clearly).
If you do a google search on 'Master Cleanse' (the lemonade/fast/cleansing protocol) AND 'liver flush', you'll see a LOT of people recommend/need to flush after doing the Master Cleanse.
What you're experiencing is VERY common/normal, and it's a great sign that your cleanse/fast is doing what it's supposed to be doing! YaHOO - Good for YOU!
Healthiest of blessings -