What Causes Toe Nails To Turn Purple And Fall Frequently?

Hi. The nails on my toes next to the big one on both feet keep falling off and growing back. There is no pain. On one foot, my 3rd toe is and has been purple for a couple weeks but continues growing. I recently noticed on my 2nd toe next to the purple one, underneath the already broken -ready-to-fall-off-nail, it was developing something purple similar to my other toe. Im worried it might be something big. Or could it be just fungus?