Hi, Holly, and welcome! I'm so glad you found us and joined in. I have costochondritis and you can be quite sore with it. When I press on the sternum it is tender. I sometimes feel like I have an extremely tight band around my ribs and chest and it hurts to breathe. My doctor has me taking ibuprofen with food to help with that.
You didn't say if you had fibromyalgia or not but, if you do, be sure to check out Fibro 101...the second thread on the forum. There are links to good info about fibro and you will learn a lot there. There is a link all about costochondritis there because quite a few members are dealing with it. This will explain it to you and help you understand it better and hopefully put your mind at ease.
http://www.mayoclinic.com/health/costochondritis/DS00626
I hope this helps you. Don't hesitate to ask questions because we are here to help you. I hope to hear more from you soon.
Sherrine