<human>: OK so pretty self explanatory.... 

When I am flirting with a guy or have an FWB (just to clarify I don't have sex like on the regular. AKA I am no whore) I am totally fine. I am talkative, out there, confidant, etc. 

The problem is when I start to really like someone and he really likes me back, I am no longer the confidant person. I over think things. I'm suddenly nervous around him, I don't know what to say, I freeze. I keep to myself (so unlike me). I just in general get really scared and nervous which results in the whole thing crashing and burning and I'm left hating myself, wondering WHY on Earth I am like that with someone I really like. Why can't I just be normal like I normally am before these feelings kicked in?

I have thought that it may be because I've been hurt in the past and I freak out and worry it will happen again? I don't know.. :( Any advice would be helpful

Can you condense the text into a few key points?
<bot>: I am bubbly and my complete total self around guys or FWB, but when a guy starts to really like me and I him, I am completely different and have no idea what I am doing. Can't understand why :(