I began to feel very very slight flutters at that time! You could very well be feeling baby, even if you second guess it for a while lol. I'm 20 weeks now and it has been amazing to feel the little flutters change to heavier pokes and prods and obvious movement! Look forward to it! Looking back it'll probably all make sense to you that it WAS your baby moving. :)
Also, as baby gets bigger, your uterus us taking up the entirety if your bottom abdomen lol. Your intestines are squished up and therefore your stomach is being squished, so there's less room. Try lifting your arms up after you eat, pacing/walking, or stretching out on the couch (if this doesn't cause heartburn lol) because it'll stretch things out a bit and give your stomach a little more room.
I havent felt my baby move yet and I'm 16 w 3 d some women don't feel baby until 18-20 weeks. I wish I did though !