Signs of preterm labor

I’m only 17 weeks so I pray to god this is normal. So far today I’ve had 3 bm. Typically I go less then that a day if I go. I also a full back ache. I don’t really have contractions to time or really a sign of contractions at all besides the back ache. I’m hoping it’s the tacos i had last night and not the sign or pre-term labor. Has anyone had days like this?