Generally for extensions to look natural we say that clients have hair long enough to tie into a ponytail, even a short stubby one. The issue with micro rings is that the rings themselves will be readily visible as your hair would be too short to disguise them well.
Keratin shrinkies are also not an option as they are 1cm long so potentially even more visible than a ring.
Keratin micro bonds may be better, but once again I would say that your hair is too short to do anything yet....
Can I ask are you still on any medication? As some side effects mean your hair is continually kept weaker than normal and we often say that you should wait at least 6-9 months after your last treatment before considering the additional weight of extensions on newly growing and potentially weaker hair.
I hope that's been of some help? If I can help in any other way contact me via http://www.nvextensions.com