I'm 18 week's tomorrow and I have a big baby belly myself. I had all bloating all up until the last like 2 weeks and I'm positive it's all baby belly now.
I was "showing" early too and I'm really skinny so I was sure it was baby. Nevertheless, it went back down around 11 weeks. It was all bloat. It's getting there now, though. I'll be in my 15th week this next week. So my bump is actually starting to form.
Right now its all the bloating. Drink lots of water to help