I have found that "rebound" relationships rarely work well. I'm also a believer that one should deal with the current relationship first before getting involved in another. Whether that means getting a divorce or living apart for a time because you never know what may happen after a cooling off period.

I'm sorry that you are feeling hurt and scared at this point. It's got to be very difficult for you, and I'm sure, very difficult for your gf as well.

I wish you all well and hope that things work out for the best, even if that means the relationship between you and your gf ends, it may be for the best for her and her children. And that's her number one priority....her children.