Hi A.- sorry to tell you this, but it could be with you for the rest of your pregnancy...I had this w/ my first pregnancy and I was not sitting at a desk all day- I was teaching so I was on my feet alot, but it got to the point where walking up hills aggravated it, or hard walking in general- i really had to curb my exercise, etc. which was a bummer...It was very on and off- I'd have it for a few days and then it would be gone for a week and then come back...it has to do with the shifting, etc. of your pelvic area and the baby putting more and more pressure on it!
I always tried to do some stretching for the area, and even some yoga- I can't say anything was a sure fix, just that this is one of those things some women have... I'm in my second pregnancy now and it hasn't been a big issue yet (yeah!!), though I'm holding my breath on that- a friend of mine who didn't have it first time aroudn is now dealing w/ it in her second pregancy. I think it all has to do w/ how the baby is situated, etc.
Stretch when you can! Try not to aggravate it and just count it as one of the wonderful preggo symptoms!!