If you are worried at all ask your DR for a scan just to check the baby over.
But to give you peace of mind, everyones pregnancy is different, some show straight away and others hardly show at all.
You used to have a 6 pack, so you had very tight muscles, so that will keep your stomach more firm for a while anyway.
When i was pregnant with my son, at 17 weeks, it looked like i just had a bit of a period bump. By 22 weeks, my tummy was still very small. Then when i hit 27 weeks, my baby appeared out of now where and i had a large bump. My little man was hiding at the back until 7 months, and then as the room in my tummy ran out, i just expanded lol.
Im sure everything is ok, but like i said before if you are worried, ask for a scan :-)
I am 31/32 weeks pregnant. I really didn't show until I was about 20 weeks, and other people didn't notice until I was at least 6 months. Your uterus isn't even above your belly button until you are 20+ weeks, and you typically don't start gaining a big amount of weight until after that either I think at 17 weeks I maybe gained 6 pounds at that point... I have gained 23 now :)
no you are not doing anything wrong. Some people just show faster than others. Apparently you have great muscle tone which is helping to "hold" things in for now, you'll start to pop soon, don't worry!