Don't Know How to Contribute to Conversation

I need to learn how to contribute to conversation. Seriously, this has been a major problem for me all of my life and frankly it's frustrating. I imagine it must be annoying to the person I am trying to have a conversation with. I'm talking with this guy on Facebook - I mentioned him in my last entry - and I really do enjoy talking with him, but when he says something like "I just got home and ate so I am ok" how do I respond to something like that? He's waiting for me to reply. I don't know what to say. I don't want to say that's good because who the heck says something like that. I just want this whole conversation thing to be easy for me for once. Ugh! I also hope he never comes across these blog entries because that would be embarrassing, haha. I doubt any of you guys would have any advise for me on this. If you do, feel free to leave it the comments. Thanks.