2 periods in one month, two weeks apart!!! HELP!!

Hi I was on my period and went off then 2 weeks later I started bleeding out the blue I bled for 4-5 days so basically I had 2 periods back to back….that only happen to me once years ago & never again until now, I don’t have irregular periods so I’m wondering what is it and hoping it’s nothing serious. My friend told me this happen to her with her second child and she found out she was pregnant, I’ve been drinking alcohol so I’m hoping that’s not the case. Any advice??