Is it normal that my girlfriend

First; stop seeking girlfriends. You can get all you need from dating [no commitments], and as many as you want.

Second; if she is telling you she is pregnant, tell her good luck with that, then say , "Bye".

If she is pregnant and goes through with the birth, demand a DNA testing. You should always do that anyway.

Worse case scenario; if it is your child, you are only responsible for the child support. DO NOT, I repeat, DO NOT marry her.

And yes, women do lie. So don't get stupid.