The IUD does not affect the accuracy of a pregnancy test. If you have had negative pregnancy tests, the odds are very good you're not pregnant. If you doubt the result, wait for one or two weeks before retesting.
It's very UNLIKELY that you are pregnant. Especially with the two negative tests. First, you should know that it takes time for pregnancy to show up on the test. With that said, it is still not IMpossible to be pregnant and have a period still.
It is possible to have a small amount of bleeding each month and still be pregnant, but it would be unusual to have that combined with negative pregnancy tests as well. I'd say you wouldn't be pregnant.
Yes. Although negative home tests due decrease the possibility, you can still certainly get pregnant. You should make a doctor's appointment for a pregnancy test. That will give you the most definitive answer possible.