New in NC

Hi everyone! I'm new to the sport and already made a big mistake. I've been running for about 5 years now and completed a couple 5 and 10Ks and two half marathons. Until recently the only biking I've ever done was around the neighborhood as a child. I also just finished a beginner swim class to work on my technique. My mistake is that two weeks ago I signed up for a sprint triathlon that takes place on July 31. The first half marathon I did without training and you would think I would have learned my lesson but I guess not. Anyway, the running part is fine (I'm also training for a half marathon in Sept) and the biking is also going well. I'm struggling mostly with the swim. I'm having trouble swimming consistently for the whole distance. I can go the whole distance alternating between the front crawl and elem. backstroke, but I don't think that's really pratical for the race. If anyone has any suggestions I'm completely open to them. If not doing the race is my best bet right now that's understandable. I'll just train until I'm ready to race. Sorry about the length of this message. Thanks for your input.
~Amy