Soft cervix at 30 weeks?

Hi everyone. Just got back from my dr who told me my cervix is softening (though not dialated at all- it's also still about 4cm long). I've slowly been losing bits of my mucus plug over the past few weeks and have had slight cramping so she gave me an exam/ultrasound. I'm only about 30 weeks and wasn't sure if this necessarily means I'll likely give birth early? Has anyone had a similar experience? My dr didn't seem too concerned but it has me freaked out!