Baby movement or muscle spasm?

FTM here...I'll be 17 weeks on Friday and yesterday and today I've been feeling slight little spasms in my lower abdomen/upper pelvic region. It's a quick light sensation that only lasts a second then it's gone. Is this just a little muscle spasm or could it be the baby moving? I know many FTM's don't feel movement until after 20 weeks so I'm not sure what I'm feeling lol