If you stop acting like a selfish kid and stop that jealousy crap (jealousy is a sign of fear, envy, and selfishness), then you will be fine. She is pregnant you big goof! Of course she has changed. Tend to her needs and put yours aside until the baby is born then help her heal from the biggest, most life changing event in her, and your life.
In short, grow up and get a grip. You don't have to act like a kid unless you want to. So don't!