I got pregnant when I was 18 and I weighed about 130 lbs. I didn’t have much money so I would zip up my pants as far as I could and stopped buttoning them in month 3. In month 4 I started wearing sweats (the cheap alternative to maternity clothes), but you still couldn’t tell. The only portion of me that gained any weight was in the mid-section. My ankles didn’t even swell. I attributed that to the fact that we didn’t have a car and I walked everywhere. I looked as if I was gaining a little weight, or getting a little chubby. I was able to pull off not looking pregnant until around month 7. But even then, in sweats and a tee, you couldn’t be absolutly sure. But month 8 and 9 it was pretty obvious.