I can barely walk

I made a few mistakes Friday.  I did some extensive stretching of my hamstrings and quite a few exercises in which my legs were entirely straight and in some cases hyperextended.  The same evening I fell asleep at my desk with my right leg hyperextended in front of me for about 2 hours.  I made it through saturday with some moderate pain during the day.  Sunday (today) was the worst so far.  I can barely walk.  I've strained something on the back of my leg behind my knee to the point that it's almost impossible to straighten my leg.  Any movement of my right leg is very painful.  The timing of this injry is extra disapointing with my 100 backstroke at U.S. Nationals five days away.  Since I'm driving some of the swimmers, I will make the trip regardless but I may scratch the event entirely and just watch the meet.  I'm in quite a bit of pain right now.  It's difficult to imagine I will be 100% ready to race the best backstrokers in the country on Friday.  I'm embarrassed that stretching of all things caused this.  I'm frustrated with myself.  I've been training very well only to do this to myself leading up to the biggest meet before the U.S. Olympic Trials.  Not good.

I had a chance to swim today but decided to give it a day to heal and do as little as possible.  I feel like the next few days will be more of the same... lots of pain