congratulations on your successful weight loss.
As you are probably already aware, your Body Mass Index is right in the middle of the healthy normal range, so your goal now should be to slow right down your weight loss and move into a maintenance phase.
Just like the weight loss phase, this maintenance phase will require a bit of experimentation to find out exactly how much exercise and what sort of weekly eating habits will help you maintain your healthy new weight.
If you are still losing weight and you don't want to, start making minor adjustments to your exercise and diet regime.
With regards to exercise, start reducing your workout times slightly or add another rest day to your weekly program.
With regards to diet, start adding back healthy calories where possible and start enjoying some foods that you like that have been "off limits". Just be careful about adding too many of these too often.
Another important thing to do is to change your goal from reaching a certain weight to maintaining a healthy weight range, say between 50 and 55kgs for example.
Most importantly, be very careful not to continue trying to lose weight beyond what is considered healthy (anything lower than a weight of 45kgs is considered underweight for your height).
In addition, don't panic or over-react if you put on a kilo or two by reducing your exercise and adding a few extra healthy calories into your diet. Just make some further small adjustments the other way until you learn how to keep your body around the middle part of your healthy target weight range.
Hope these thoughts help and please let us know how you go and what you discover works for you.