I feel like I'm going to be sick because my ex who is the love of my life is pregnant.
Why does that upset you so much?
I'm not sure if my current girlfriend will deal with me and will keep me.
If you can't get over your previous relationship and can't handle the fact that your ex has moved on, you shouldn't be in a new relationship. It's inconsiderate to your current girlfriend since you are more focused on your ex than her.
How is it wrong to think about my ex? I shouldn't need to be focused on my current girlfriend all the time.
It is wrong because thinking of another person while you are in a relationship can hurt the person you are dating. How would you feel if your girlfriend was thinking of another guy while she was with you?