Match all lines starting with a space up till a line that doesnt start with a space

So I have a few lines like such:

tag1:
 line1word1 lineoneanychar
 line2word1
tag2:
 line1word1 ....
 line2word1 .....

I am trying to build a java regex that extracts all the data under the tags. i.e:

String parsed1 = line1word1 lineone\nline2word1
String parsed2 = line1word1 ....\nline2word1 .....

I believe the right way to do this is using something like this, but I haven't quite got it right:

    Pattern p = Pattern.compile("tag1:\n( {1}.*)\n(?!\\w+)", Pattern.DOTALL);
    Matcher m = p.matcher(clean_data);
    if(m.find()){
        System.out.println(m.group(1));
    }

Any help would be appreciated!

Could be something like that

public static void main(String[] args) throws Exception {
    String input = "tag1:\n" 
            + " line1word1 lineoneanychar\n" 
            + " line2word1\n"
            + "tag2:\n" 
            + " line1word1 ....\n" 
            + " line2word1 .....\n";

    Pattern p = Pattern.compile("tag\\d+:$\\n((?:^\\s.*?$\\n)+)", Pattern.DOTALL|Pattern.MULTILINE);
    Matcher m = p.matcher(input);
    while(m.find()){
        System.out.println(m.group(1));
    }
}

Remember to escape \\ in your regex.

\d is a number

\s a space

(?:something) is for making a group that won't be a real 'group' in the matcher