no hun 3 weeks is so early for you to see or notice any difference, if anything you might have bloating but that's it. your uterus is still in your pelvis at this point. Congratulations and good luck :)
At three weeks most women don't have any symptoms and it's rare to even know you're pregnant at that point. I'm assuming this is your first so you won't see many changes in your belly for a few weeks yet; you might see them within a month but others won't notice.
at 3 weeks that is like when the sperm and egg have gotten together and maybe implanted in the uterus, that is about it. You wouldn't notice anything possibly impantation bleeding but other than that, not much. at 6-7 weeks I was super bloated and then around 8-9 weeks my real symptoms kicked in.