Frustration!

I am a new swimmer.  I've known how to doggie paddle and tread water for most of my life.  Only recently did I learn to do the front crawl in preparation for a sprint triathlon I am completing in July.  I've been swimming 2 times per week at the local Y during upon swim time.  I still am not confident enough to go during lap time.  I don't want to inconvenience people that are serious and good.  I'm serious just not good, yet.

So the sprint triathlon swim distance is 500 yards or meters or something like that.  The plan I am following indicates a person should be able to swim 50 yards without stopping.  Okay, I can do that.  However, the first day of training (which doesn't start for me until April) has a 1,550 yard swimming total!  Do you think it might be a typo and the prereq should be 500 yards?

I still am getting winded and only swimming between 250-300 yards per session.  That takes me about 15 minutes.  I can't go non-stop 250 yards!  I am frustrated and not sure what to do.  I can continue going twice per week and push my distances but will I ever be able to swim for 1,500 yards??? I realize that I am new at this but why is it so difficult.

Okay, I am done sucking my thumb and will get back to working and finding a way to make this work!