7 weeks and showing?

I am pregnant with my second child. I am 7 weeks pregnant currently. With my son I gained 70 lbs total. I was 95 lbs when I got pregnant. I am 115 lbs after the baby. Well, I may be loosing it but I am already showing. I know it cannot be baby due to the size the baby is. I am naturally a small person but, I honestly look like I am 14 weeks pregnant again. I am on progesterone and have heard it can make you gain water weight. Should I be concerned I am gaining belly weight so fast? FYI I don't eat bad.