2 days before half ironman....am I ready?

So, some background info before I get into this....I have been training for this race since January and everything was going pretty well....my swimming is average, its improving and I'm happy with it, my biking is great, I think I'm pretty good at it seeing as I've only been road/tri biking for alittle over a year. Running on the other hand is a constant struggle....I have been injured on and off ever since I started running regularly in college, I've been to all kinds of people, lots of physical therapists, sports medicine doctors, chiropractor....anyway its always different injuries and I never get to train consistently for more than a month before I have to take time off for something. Oh, I have also tried lots of different types of shoes...I have extremely high arches...and custom orthotics...Anyway! things were going okay with the running stuff up to 2 weeks ago when I started to get this pain in the top of my calf area....not good, this is right before my race taper, then I went out for my last long ride before the race which was supposed to be 3hrs and I felt the pain then too....that did it for me. I stopped riding and pretty much have just been swimming and going to yoga class (a huge effort for me, I'm not a yoga type) ever since last weekend. My leg has since been feeling fine....but why wouldn't it I haven't been doing ANYTHING...but I feel like crap and feel like I've lost all my fitness for my race, I had a 6 hour goal in mind but now I'm so depressed at the idea of going out there and not doing as well as I know I could have done. What if I end up not being able to run and have to DNF....that would suck. Or even worse, what if I just hurt myself more and am unable to train for a month after the race?! I don't know what to do....to race or not to race? which would feel worse? whats better for me? I don't want to jeopardize my ironman training either. How much fitness do you lose when you take a week off anyway??