Plus sized pregnancy question

Okay, so im kind of a big girl and ive got a tummy on me. No lie,ive basically been holding it in for the last 5 odd years but pregnant,lol. 
People normally start showing around 12 weeks and im coming up to 13 weeks now and finding it hard to hold in my belly anymore. But i dont think ive actually got a proper bump,i dunno. Anyone out there know ihow i can tell the difference between bump and fat??