IMO you'll be fine! The training program I followed for my IM always had us doing time, not distance. Since I wasn't biking as fast as they were assuming, nor running the 7:30 min/miles they assumed I was, I always added about 30 min to each bike workout and 15-20 min to each run workout. I really think you'll be fine, tho. Keep at it, taper like you should, and think of race day as your celebration for all the hard work you've put in.