Two flats...out of race

Had my second sprint tri yesterday. Blew my PB in the swim getting out of the pool just before 8 minutes with my arms practically falling out of my shoulders. Quick transition and jog to the bike...feeling good...tackle the hills...get low against the wind....*pop* Had a blow out going downhill. Tried to steer off to the side but it ended up being a workout in bike dismounting while on the move as I crashed into the ground. Tire was twisted and took a while to get off of the rim. Finally got it all fixed up and pumped up with my Co2 and noticed there was a bit of the tube wrapped up in it. Partially deflate and go at it again...all set. Wrestle the tire (had to be the back tire, of course) back on the bike...*POP* Over-inflated it so now I'm stuck with no catridges and one more tube. Feeling deflated, not unlike my tire, I start to walk with my bike, the two miles back to the race start (thank goodness it was a loop) just as my training partner flies by and asks if I have everything I need. I say I need a cartridge and he pops one out and gives it to me. Life saver! I'm so freaked out about overinflating (plus there's a big hole in my tire) that I'm riding on a really low tire. Complete the first lap, then the second and realize I'm the only one on the course. I called it a day. I can swim through pain, run threw pain but I can't freakin' ride with a low/flat back tire. I hate my bike.