On and off periods.

For reference: I am 18 this is my first IUD. I have had it for a little over a year. I have one sexual partner who I have dated for over four years.

My periods stopped for a while then started back on an irregular basis for about 3 months. I talked to my gyno and they said that if I could feel the strings and i didn’t need to worry. Now my periods have stopped again. Has anyone else had this happen. Should I be worried?

Another question is are you guys using more than your iud for protection or do you rely solely on your iud?