I had a Paragard IUD for 5 and a half years (just had it removed yesterday, in fact), and used a Diva cup during my periods for all of that time. Never had any problems with it. With the IUD, I did take care to always break the seal before pulling the cup out, which took some getting used to; my cervix is up in Canada somewhere which made it sometimes challenging to hook a finger over the rim of the cup (just squeezing the sides never broke the seal for me). For me, it was easy to break the seal if the cup was pretty full because it seemed to sit lower, but on the lighter days near the end of my period it would ride up to hug my cervix and was sometimes harder to reach and unseal. But it was all manageable, after a short learning curve. The past 3 or 4 cycles, I've been alternating between the Diva cup on the heavy flow days and Thinx underwear on the lighter days, and that's worked well.