BF, the lingering affects of the downfall of our marriages and the insecurity that it has embedded into us is amazing.
IMHO, you have to find your confidence again and believe in the "Us" factor. If the two of you are meant to be then you will,if you are not then you won't. Simple as that.
That whole conversation sent red flags up all over the place that you still have work to do on yourself and your feelings. The responses that you gave her were not those of a confident man secure in his relationship. They were filled with fear and insecurity.
You do not know the reasons for her fears, you don't know why she needs space, and you don't know what she is going to do. Trying to figure out the answers to these things is difficult and you guessing those reasons make it even harder.
Maybe you simply need to have a little Blind Faith that everything will be ok.
