Not a happy bunny

In October last year I entered a long distance triathlon (2.4 mile swim, 112 mile cycle and 26 mile run).
I started training in earnest for this in January.
My training hasn't been as good as I'd have liked it to be but I have managed to complete a number of races along the way which have shown that what training I have done has made sure that I should be able to get around the course within the required time.

I'm fortunate that within 15 minutes of running I can be on the outskirts of town and running on quite roads and lanes.
Yesterday I headed out for a planned 3 hour run. I headed out into the local countryside along a quite road before turning off with the intention of heading along a lane to one of the nearby villages before turning back and retracing my route.
One hour into the run and my left knee suddenly became painful.
Last year I had a problem with the same knee and saw a physiotherapist about it. He couldn't find anything mechanical wrong with it but between him and the lady who comes into work to give back massages it was discovered that the illio-tibial band in my left leg was very tight.
Jo, the lady at work, gave me some stretching exercises to do and told me to swim front crawl rather than my usual breaststroke, while the other physio told me not to run for 6 weeks.
Well things cleared up and I was able to start running again.
Up until now I've not had any problems although after a race a few weeks ago I had a sports massage and the woman that did the massage told me that the IT band in my right leg was a bit tight.
Yesterday for some reason the left knee decided to play up big time. In fact I managed to carry on running for another 20 minutes before I was reduced to walking in order to avoid doing any further damage and then phoned home to be picked up in the car.
The pain went as soon as I stopped running but last night having had to do a 20 minute walk to collect son from the club he goes to I could feel a few twinges in the knee.
Today I'm going to try and get an appointment with my GP, will be a good opportunity to update her on what's happening with my transitioning, and see if I can get a referal to someone to get the knee looked at.
The last thing I want is to have to stop running as the race I've spent this year getting ready for is only 5 weeks away. Of course I also don't want to do serious damage to my knee and end up not being able to run for even longer.
Hopefully this will be a minor hicup and not something serious.
Hopefully!