Irritation from Cup?

hello dear Cup users, I had a question for you. Have your cup created irritation to your down there? I feel like mine is and I don't know why. I used it for 5 years now, always taking good care of it, boiling it 10-15 minutes before use and after de Period, washing it with the cup soap when emptied and so on. But, since 4 months now, every time I used my cup I dome out with pretty bad irritation that calms down 1-2 weeks after I stop using my cup. For my recent period I switched back to tampon and pads to see, and as expected, not a sign of irritation. Now I hate those tampon and pads and would love to return to my cup, but not to the price of irritation. Is it because my cup is probably old? or could it be just my body rejecting it? For those of you who lived this, what did you do? because I don't want to invest in a new cup if it's going to give irritation again :) thank you for your answers :)