Breast discharge advice please?

Can anyone help?

I noticed today my breasts have started to leak fluid. Its kinda clear straw coloured. I have a mirena coil and have had no periods for many years. This happened before when my coil was changed but that was in may last year and vanished after a few months. My boobs have been sore for the last week and have got a bit bigger recently. Has anyone any suggestions as to what's causing this please? I'm a bit worried. Thanks in advance Xx