I guess it depends on the size/freshness of the lime. I make limeade on a regular basis and 1 lime will produce approx 1/8 cup of juice - so I'd try 4 or 5. Make sure limes are fresh and roll them well before cutting to juice

Certain types of birth control can cause this. Has anything changed that you are now using? If you are not on birth control medication then I would make an appointment with a medical professional.