So I've definitely felt the baby move a couple times before, always flutters like a butterfly but…

So I've definitely felt the baby move a couple times before, always flutters like a butterfly but short and quick.. Tonight my fiancé put earbuds on my belly and turned on music for the first time, and I'm feeling constant flutters on my left side.. I just can't tell if it's baby or possibly something else (like muscle spasms) cause it's pretty consistent and a lot longer than the first couple of times..?