I got my IUD in 3 months ago and I freaked out too when I couldn't feel the string after a couple weeks. I check it a couple times a week in the shower and one day, I could not feel it. I freaked my guy out by telling him that. Later that day, I checked again, and it was there.

Sometimes the string seems to lay against the flesh inside. At least, that's what I've noticed. Some days, I can find it easily. Other days, I can barely find it or not find it at all.

When I first got it, I bled like crazy but that's because the IUD was pressing against the inside of my cervix. My OB Gyn at Planned Parenthood checked it, wiggled it, and I felt instant relief and bleeding stopped.

At 6 weeks, you really should go back to your doctor to have them check it. They told me to come back within 6-8 weeks from insertion.

Best of luck.