How do I become more open with my friends?

I have a lot of problems and I'm usually very upset. My friends don't rea;ize this, though because I'm always smiling and "happy" and whenever someone asks how I am, I always say I'm good. My one friend-- friend #1-- has been constantly been telling me to tell people how I feel and to be more open since the day I told her about some of my problems. Well, friend #1 had been bugging me about it, so I went and complained about it to friend #2. Friend #2 started asking me why I'm not open and now she's acting like friend #1. This is what friend #1 had told me: yeah dee, i highly doubt that. again you dont realize but with you there is always something... to be worried about. So now I have two friends bugging me to tell people how I feel and what's going on. But there's a problem; I don't know how to be open. I've always put others first. It was-- and still is-- very rare for me to think about myself.