I had the same problem. I did not get a bump until a few weeks before I delivered. I lost weight (40 lbs) so everyone noticed that and you couldn't tell at all I was pregnant.

Is this your first ? with my first I was a week shy of turning 7 months and no one could tell I was pregnant and I was still 119 lbs but had a little budge on my belly which wasn't there before but as soon as I hit 7 months by belly grew from leaps and bounds but when belly is bigger u r back aches more . but don't worry u will show soon enough. I was a little upset when. I wasn't showing yet like others but realized afterwards I was thankful that I didn't get belly fast as I said stated above when belly got big back ached like crazy