Been on anti-biotics since Friday morning and still feel rough.Tender lower back etc,and a sort of spaced out feeling.Also spent all night having odd episodes of feeling really frightened,which I guess is connected in some way? How long do the anti-biotics normally take to kick in? (I've only had one before and can't remember,although I think it was quite fast) Also I wonder if this was actually ticking along for a while and then suddenly got worse,can you have a low grade UTI?