You just need to go through the anxiety and not think about it so much. Thinking makes it worse.

You should be mad at your boyfriend but I don't think you should punish the kid for existing. Fears don't disappear and if you go on vacation for 10 days and avoid them you are only reinforcing the fear. I think confronting the fear is the best way to go about it. I went on a trip (just got back 8 hrs ago) and experienced what would be crippling anxiety. I could have spent a lot of time thinking about my fear of meeting and talking to strangers or I could persist through the anxiety and deal with the physical symptoms after the fact. I am experiencing sleep deprivation, have puked recently, and have had bowl/heartburn for the past 5 days. The whole time I was playing [a card game] my body was under extreme stress which led to the physical manifestations of anxiety. It is impossible to teach my body and mind that its okay if I don't go through with the exposure.

Maybe I am being harsh, but it doesn't make sense to stay in a committed relationship with someone who has children and not be there for the kid when they visit. You're speculating too much and not allowing yourself to live in the present. /IF/ the child decides to stay with the father, you can deal with it when it comes up. Don't worry about a problem that doesn't exist yet.