I've been to a few proms. I am embarrassed to admit that I had been looking at dresses since I was 13 yet it still took about 6 months to ultimately find one. You should definitely get out early looking for dresses though especially if you are really tiny. The alterations took two weeks for mine.
As for the pre-prom, a similar situation happened last year. I had just gotten over a huge fight with one of my best friends unfortunately the other three were still not speaking to me. I ended up just having my family over and taking pictures with them and my boyfriend because it was just way too hectic to go to my friends house. It was much more special for me I think.

Oh man, the same thing happened with my transportation. I so wanted a limo and my friends were all planning to put money together and get one. Ugh, they never got their act together and by the time they let me know, it was too late and all my other friends had filled up their limo. I was heartbroken and I regret it. My boyfriend ended up driving though and it was okay in the end. Haha, I got to handle the music!