Regular expression not worknig - regex

Question

I am trying to create a regular expression in javascript with the following rules:
At least 2 characters.
Should have at least 1 letter as a prefix and end with a . or have or - and then have more letters.
The following strings should be legal - aa, aaaaa, a., a-a, a a.
These should not be legal - a (too short), aa.aa. (two dots), aa- (after - should be another letter).
I don't know what I'm doing wrong here but my regex doesn't seem to work, as it is legal yet no word matches it:
(?=^.{2,}$)^(([a-z][A-Z])+([.]|[ -][a-zA-Z]+){0,1}$)

Answer 1

Had to re-write it completely to cover op's comment. The new regex would be:
^[a-zA-Z][a-zA-Z]*[ -][a-zA-Z]*[a-zA-Z]$|^[a-zA-Z][a-zA-Z]*([a-zA-Z]|\.)$
Explanation
1st Alternative ^[a-zA-Z][a-zA-Z]*[ -][a-zA-Z]*[a-zA-Z]$
^ asserts position at start of a line
[a-zA-Z] Match a single character present in [a-zA-Z]
[a-zA-Z]* * Quantifier — Matches between zero and unlimited
times(greedy)
[ -] Match a single character - or a space
$ asserts position at the end of a line
2nd Alternative
^[a-zA-Z][a-zA-Z]*([a-zA-Z]|\.)$
^ asserts position at start of a line
[a-zA-Z] Match a single character present in [a-zA-Z]
[a-zA-Z]* * Quantifier — Matches between zero and unlimited
times(greedy)
([a-zA-Z]|.) Match a single character present in the list below
[a-zA-Z] or dot
$ asserts position at the end of a line