Is it true that if you bleed on the iud that you are having a miscarriage, even if it isn't that much blood but i am having sever cramps?

Not at all: If you think you might be pregnant check then check a home pregnancy test. They are cheap, reliable and available at any pharmacy. Irregular bleeding with an IUD is common and certainly does not mean that someone is pregnant or having a miscarriage. Consider chlamydia testing if you are with a new partner and the spotting is a new problem.