I know this is a scary time--it was for me! This happened with our son and I just want to reassure you--he is perfectly fine and healthy. I've come to find out that this is a very common thing (so are dialted kidneys, which my son also had). I think with all of the technological advances they have today, they are just able to see more things and sooner, which is a good thing, as then they can prepare for things. So, try not to worry too much and wait to see what they see at your next ultrasound. They may have you have a level 2 ultrasound (a 4D one, which is really cool, but when you're there and your scared that it might be something bad, it's not as fun as it could be!). We had ours done down in Denver and I felt like that doctor did a great job and really knew what he was talking about. Of course, you're always going to worry about these preciouls little souls that we have been blessed to take care of...but try not to and know that doctors don't know everything and sometimes things that "could be" a problem, turn out just fine. If you want to e-mail me, with any other questions, feel free to.
Take care of yourself!
ps...I'm sorry your doctor sent you on your way without more of an explanation and you're next appt isn't until July 5!