I was told within the 1st year most women will not have a period anymore. I've only had mine for 2 months, the last period I had lasted 2 weeks, and I've had spotting of different sorts off and on since I've gotten in. I've never been able to feel my strings, the doctor believes they've been pushed into my cervix but it's still in place.
If you go to you GYNO you can have them look for the strings, they could just be pushed up, or behind your cervix. They can do a sonogram to make sure it's still in place and hasn't expelled.