The answer is that this varies from woman to woman. Depending on how overweight you are, you may wind up looking very pregnant, where you might also just look larger than before. This is not just for women who are heavier, because there are plenty of other women with bellies who fall into the "I don't look pregnant." category.
That said your belly will change. Whether you look like a well rounded belly, all out front, no one can make that prediction. The changes will be most evident to you and those who know you well, particularly when naked.
The question really comes to how you let others know that you're pregnant while you're in those in between stages of showing. The first thing to do is to tell everyone you're pregnant (when you're ready). Then when possible, remind them about your pregnancy. Go to maternity clothes rather than wearing your normal wardrobe, it helps to emphasis your pregnant belly. This can help without having to resort to t-shirts that declare BABY with an arrow pointing towards your abdomen, unless you want to wear that type of shirt. (They also make buttons.)