Period-like cramps pre-labor?

I’m pregnant with my first child (currently 35 weeks 5 days) and just spent all night with what felt like period cramps. Nothing crazy and definitely not what I expected a contraction to feel like. They’re super low where my underwear line is and not exactly measurable (mostly constant, occasionally go away for a while). Did anyone have this and was it an early labor sign? If so, how long after this did you go into labor? I called my Ob and waiting for a return call but unless this is a real emergency, I really would like to avoid going to get seen today (crazy day at work). Obviously if I’m going into labor I won’t have a choice but from what I’ve read, most women who have this don’t go into labor for weeks after. What has others’ experience been? Thanks!