A small amount of clear or watery fluid that appears only when both nipples are deliberately squeezed is common and is often physiological rather than a sign of disease. The squeezing itself is what produces and maintains it. Evening primrose containing supplements are sometimes associated with breast tenderness and odd shooting sensations, so a link with the tablet is plausible. What matters more than the fluid is whether it comes away on its own without squeezing, whether it is from a single duct, and whether it is blood stained.
Next Steps
Stop squeezing or checking the nipples for two to three weeks and see whether it settles. Speak to the doctor who advised the supplement about pausing it, and book a clinical breast examination if the discharge continues.
Health Tips
Spontaneous discharge that stains your clothing, discharge from a single duct, any blood in it, or a new lump should be examined promptly rather than watched.