Stuff hanging out of cloaca?

Barnaby hasn't been eating for almost 3 weeks. A few days ago he was starting to get very lethargic and not moving around as usual so the day before yesterday me and my housemate tried to force feed him (not super successful) and again yesterday (pretty successful), and he has been swimming around again more normally since those two occasions. I decided to give it a break today and try again tomorrow to reduce the stress to him.

But - yesterday, and still all of today he has had some kind of clear substance hanging out of his cloaca, and his cloaca is really swollen and open, I can see right in it, totally abnormal. I thought it could have been eggs or something (and that he is a Barnabette), but it's just been hanging there for two days now, so I just don't know.

Background - He lives on his own, he's always been really skinny, he's probably at his fattest he's ever been at the moment. A few weeks ago we moved house and then about a week ago now he moved into a new bigger tank, and a few days ago I swapped all his plastic plants for real plants. And his cloaca was no where near looking like that previously. His pH is 6.9, Ammonia 0, Nitrite 0, Temp 23-ish and I broke the Nitrate bottle.

The first two pictures were taken yesterday and the third one just now (His cloaca appears to be considerably more swollen since yesterday, but the stringy stuff looks the same)

The temperature is pretty high and it should be around 18.
You also say he's at his fattest now. I'm not sure but it could be that he has something inside him he tries to poop out. I think that's also the reason he won't eat very well.
I would suggest putting him in the fridge and see if something gets out. (They poop more often and easier in there and it slows down the metabolism)
I don't see gravel but is there something he could have possibly eaten?

About fridging:
Axolotl Sanctuary

Hi Morrison, there's nothing at all that can fit in his mouth except for bits of his new plants. I've been trying to avoid putting him in the fridge because firstly, we've had 2 fridges break in the last 3 weeks, and secondly because I really want him to eat, and that's the last thing he'll do in there and then thirdly because I used to have two contaners to swap around but now I only have one. But just now I have done it away.

I need someone to tell me if this is completely abnormal and if they know what is causing it!

Yesterday the stringy stuff turned green (making me think it is bits of plant that he has digested), and his cloaca became considerably more swollen yet again. Today the stringy stuff is gone, but his cloaca is SO SWOLLEN. It's not even just his cloaca, it's all above his back legs as well now. He's also started having his mouth slightly open constantly, which isn't normal either, I imagine it's because he's in pain. Oh, his tail is now curved a little bit sometimes as well.

These first two pictures are from yesterday, showing the green stuff and increased swelling:




And these two are today, while he was in his fridge container, showing how fricking swollen he is now (arrow is pointing to the bulge above his legs). It is sooo abnormal looking that you can see right into his cloaca, you see?




I've put him in the fridge now because I'm sure he is in pain, and maybe the cold can reduce the swelling. But I'm at a loss for what is causing it. Infection? Allergic reaction to the plants? Cancer? (but then, it seems far too uniform to be a tumour) I don't know, has anyone seen this before??!

I have no idea what is causing this, but looking at the pictures of the increased swelling I would advise you to take your axolotl to a vet as soon as possible.