It's fine. I didn't show with my first until about 20 weeks. I got my first stranger comment from a drunk guy at 26 weeks. Everyone shows at a different time.
No reason to be worried just because you don't have a bump. It's still early, especially for a FTM. Enjoy wearing your regular clothes for a little while longer!
There is a HUGE variation of normal. At 13 weeks your uterus is just starting to come out from behind your pubic bone. If this is your first child it's absolutely to be expected. I had no semblance of a bump with my first until well after 20 weeks.
Definitely not something to worry about, if you are having regular prenatal appointments and they tell you things are progressing well then don't stress. A pregnancy book is definitely helpful so you don't worry yourself about too much.
Hey. I'm 16 weeks and I too have no bump. The only time I can tell is in the morning laying down if I have to pee. I thing for a lot of women with their first it takes a lot longer. I'm a little thicker and I think my ute it tilted towards my tailbone so it will prob be a lot longer for me to have a sufficient bump. It sucks but the docs keep saying everything's fine which is very reassuring. Hang in there I think eventually we'll be wishing we didn't have one at a all.
Re: Should I be worried?
I suggest picking up a pregnancy book.
My Ovulation Chart