I have a pool party to go to tomorrow?

yea a shirt and shorts is fine. lots of ppl do that. Just don't be one of those people that wear their shirts into the pool because that would look weird and you will just be showing off your insecurities to everyone. Anyways, most people understand that not everyone has a great body and they won't judge you for your weight. Just try to have fun and don't spend the whole time thinking "omg what do they think" bc chances are they aren't even thinking about you. Just let your personality be more prominent then your weight!