Hi. My Son Who Just Turned Two In December Is

Hi. My son Who just turned two in December is sick. It started about 730 pm tonight and he said his back hurt. 745pm his back hurt then he puked. He puked a decent amount one more time and has dry heeved 6 times as well now, less than 6 hours since it began. I am having him sip on pedialyte when he wakes up but he's puking a white foamy substance and I wanted to make sure that was normal. I've never puked like that before myself. Also, him having back pain is concerning me but he hasn't complained about it since 745pm. Thanks