Unless you treat ITBS it will just continue to get worse. I suffered for months before visiting a phsyio and accepting I needed to stop running until I was pain free. A physio will be able to address the underlying causes of the ITBS (usually tightness in surrouding muscles) and loosen everything up. He/she will also be able to suggest targeted exercies to correct any issues. Foam rollers can be useful for stretching the IT band but they are painful. Don't bother visiting a doctor unless they are experts in sports injuries - go straight to a good physio.
I've had niggles in the same place as you for a few weeks and it seems to have progressed on from a lower back issue. I saw a physio this week and he said the stiffness in my back was causing the sciatica, which in turn was caused by sitting down too long in the same position at work. If you haven't already seen a physio, see one. If only to pinpoint the cause of your sciatica. Hopefully it's nothing serious!
I did this one too, Marmite. I forgot to take my garmin and didn't realise that the times were on the screen at the end, so have no idea what my finish time was. I also went wrong on the run course as I turned right at the little wooden bridge because there was no marhsall, no other runners in sight, and I didn't have a clue! I wasn't the only one, thankfully, and they sent a marshall down some time after. But apart from the total stupidity on my part, I enjoyed very much!!