I have an 11 week old golden retriever puppy who seems to be rather sick at the moment.

Last night, she woke me up around 5am (which is very unusual for her since she always sleeps through the night) and obviously needed to go out. I took her out and her BM seemed to be kind of runny, but it was hard to tell since it was dark and I didn't look closely. Then she woke me up again around 6:30 and this time it was very liquidy and she was straining a lot. From then on, she kept needing to go out at least every half-hour to hour, and it was the same thing every time.
I gave her a little breakfast and she ate it, and I thought it was good that she still had an appetite... I also called the vet and they basically said not to worry. She has had 2 sets of shots so far, and they said it was unlikely it could be anything serious. They said to call back Monday if she was still having problems.
Then around noon I had to leave for about a half-hour and when I came back there she had vomited everywhere. This is when I started to get really concerned. She vomited again about an hour later and still had diarrhea too. I called the vet again and they said the same thing as before -- since she's had 2 sets of shots, it's probably nothing to worry about.
I'm worried though!! She's also more lethargic than usual and is sleeping a lot. What do you all think I should do?? This is my first puppy so I just don't know if I'm being overly paranoid or what... I've just been searching all over the internet and keep finding things about parvo and other scary things, but I have no idea if I should be worrying about that since she has her shots. Also, I'm supposed to be going out for 2-3 hours tonight and I'm going to feel so awful leaving her... Anyway, your advice would be appreciated!
-Sara-