Sensitive sore nipples suddenly after 5 months BF/pumping?

I have been BF/pumping for 5 months now. The first month was very painful to be expected but since then it got much easier and little to no discomfort at all for the past 4 months. Suddenly now at 5 months my nipples are sensitive, irritated and pumping is painful. I have to stop before 15 minutes. BF seems tolerable for now. This has been going on for a little over a week. I am mid cycle could this have anything to do with it? Didn’t happen with any other previous cycles though. Please help!