Welcome to the site Danny. Couple of things here.
Learn how to use the search function. Don't worry, I'm not saying that to be a dick, just letting you know how to find stuff on here. Look at the top right side of any page and you will see the google custom search box. Type something in there like bed rust and you will see lots of threads come up. Usually within a few minutes you can find what you are looking for. Sadly for you, you're not alone but it does look like you can fix it. See the thread I copied below and scroll to post 47 to see what others have done to repair.
When you find a thread that is the same or similar to yours, post your questions there and not in a new thread. People subscribe to existing threads so you get more responses, plus it helps keep similar problems together and makes search in the future easier.
Add in your location in your signature. Helps to know where you, are like if you live in the rust belt, so others might know why it happened.
Lastly, rust proof your vehicle. I don't mean keep it really clean or park it in the garage because that doesn't do anything to stop rust from forming, I mean spray the entire truck with a rust inhibitor to neutralize the rust properly. Take it somewhere or do it yourself but that's the only way to really stop any more rust from forming.
If you just bought a 13 year old truck I am guessing you don't intend on selling it soon. If you have a truck that is rusting right now imagine what it will look like in a few more years if you don't neutralize that rust.
Good luck and welcome to the site.