So it took me about 7 weeks of aching and pain to actually look down below and what did I see, a big, mutated purple thing! Midwife has confirmed it's vulva varicose veins and there's nowt I can do about it. So that explains all this pain.
Anyone else in the same boat? It'd be nice to know I'm not the only pregnant lady walking about with the most hideous undercarriage you could imagine.