Good luck - in my case, my GP was equally useless - when I phoned after two weeks, having heard nothing about the 'urgent' appointment they'd promised me, the secretary admitted they hadn't actually got round to asking for one yet. :( And this was when, like you, I was losing large amounts of blood and largely unable to eat anything (or rather I could eat it; just digestion was agony and impossible).
My GP also gave me loads of advice all of which I now know was absolutely the wrong thing to do eg she suggested I drink lots of milk - with UC, a reaction to milk is often the cause, plus milk is a very complex foodstuff and hard to digest if your digestion is not working properly.
From my experience, lots of b vitamins (to aid digestion and stress) in whatever form you find easiest to take, iron (as you're losing so much blood), and a general multivitamin all helped. (A liquid iron etc supplement called Floradix is expensive and weird-tasting, but the easiest to digest and v effective.) Plus I took St John's Wort (natural anti-inflammatory and anti-depressant, and a natural herbal tranquilliser (something like Natracalm, which contains passiflora if I recall correctly - just helps to control the physical stomach churning caused by stress).
In terms of diet, your poor insides are completely inflamed and bleeding so you want your guts to have to do as little work as possible. I made the mistake of trying to eat high fibre foods initially to soften my stools/regularise my digestion - I could feel every single mm of brocolli or whatever as it scraped through my ulcerated bowel, like sandpaper over an open wound. Ouch. Personally, I found 'soup' made of boiled white rice with boiled chicken/plain white fish, a good basic diet, adding (but removing) carrot/onion etc to the cooking water for nutrition if desired. Plus white bread was a good staple food for me, personally, though I know that some people with UC may have problems with wheat. It's very, very boring as a diet, but does allow your gut time and strength to heal, and rice and small quantities of light protein are unlikely to upset even the crossest bowel. Apple juice, ribena, and umlimited quantities of camomile tea are also great. :) Needless to say, avoid spicy food, and alcohol, but I'd doubt either are on your list right now anyway. I also gave up caffeinated drinks when diagnosed with UC, and have not had a cup of tea/coffee for the last 15 years! - don't know whether that is essential, but it's certainly a good idea to reduce caffeine, too. Re stress - try to sleep/rest - you are ill and NEED to make recovering your priority, rather than soldiering on and making yourself worse.
DO nag your doctor. Whilst your symptoms do sound like they could well be UC, as I'm sure you're aware, they could also be something less 'pleasant'. A delay of a month or more in which you are losing large quantities of blood is not acceptable, and don't let them fob you off. I guarantee the specialists at the hospital would regard you as a priority case and would be happy to see you immediately.
Hope you start to feel a bit better soon, and get your appointment. :)