Possible contractions...should I skip taking Unisom before bed?

I'm 38 weeks and 4 days... I'm starting to have lower back pains that kind of feel like cramps. I know this is an early sign of labor and contractions could start this way. Every night, I take a B6 and a Unisom for nausea. The Unisom knocks me out, and I'm worried that I'll go into labor tonight and not know because I'll be asleep lol. Am I overthinking this?? Or should I skip the Unisom tonight to be safe and just deal with the nausea tomorrow?