Tummy measuring bigger than normal

I went in for my 24 week check up last week and when my ob/gyn measured my tummy it measured in at 29 weeks. This is my second pregancy and my first pregnancy was naturally conceived faternal twins. I have had five ultrasounds and they all show one baby at normal size, but it has been feeling like twins since my fourth month. However, I've never been pregnant with just one so I don't know if what I am feeling is normal for one.
When I got pregnant this second time I was 20 lbs. lighter and 4 dress sizes smaller than I was with my first pregnancy, but I'am wearing the same maternity clothes that I wore at this exact same point in my last pregnancy. I also started to notice my appitite reduce in my 4th month which happend in my first pregnancy.
If anyone has any info or advice, I would appriciate any feedback.