Hi everyone!

I'm having some trouble with headings. My document looks something like this:

1. Introduction
1.1 Bla bla
2.1 Bla bla bla
1.2.1. Bla bla bla
1.2.2. bla bla bla
3.1. bla bla

2. Methods
1.2
2.1.1.

It seems like the Heading 2 is "inverted", displaying 2.1 instead of 1.2. I want my document to look like this
1.
1.1
1.2.
1.2.1
1.2.2.
etc...

How do I fix this mess?! Thank you for all your help