hi there, yes it is confusing:) you certainly can get pregnant immediately after mirena removal, so as you have had unprotected sex, that is a possibility. I would continue to do pregnancy tests every few days, or get to the doctor and ask them to do one for you. Even though it is possible to get pregnant, it is also likely to have a miscarriage because you need good amounts of natural progesterone to keep a pregnancy going, and as mirena seems to actually reduce our own bodies' amount of progesterone, it is sometimes the case, unfortunately that a misscarriage will happen. For people that actually want to get pregnant, they should really wait a good 6 months before trying, because the hormones will take that long to get balanced, at least.
Some people do have a period shortly after removal, but others are just generally bleeding due to the removal proceedure itself. Everyone is a bit different so there is no real way of knowing if what you had was a small period or not. For sure though, there is no way it would be a "normal period" in the sense that your body was working as usual etc, because it is impossible for your system to function "normally" while it still has residue of the mirena chemical inside it. By definition your hormones would be in some kind of altered state.
To compound the problem, many people dont get a period for more than a month after removal, so the fact that you are late does not necessarily mean that you are pregnant, it could just be another sign of your hormones just trying to sort themselves out. To give you an example, i didn't have any bleeding after removal, just a day or two of light spotting, then nothing for about 6 weeks! Other people bleed for a couple of weeks, then nothing for 5 or 6 weeks, and then others have different symptoms again - so there is no right or wrong way for the body to react, it just does what it has to, to try and rebalance itself again, which takes time. some people have had nausea etc but it has turned out they are not pregnant, but others have been, so again, it is a difficult time for you and your body, and impossible to tell by going just on your symptoms.
I know you are worried and i am really sorry that what i am saying does not really give you any definate answers, so that is why you should probably get to the doctor to get a proper blood test, or continue with your preg. test kit usage in a few days. sorry i cant be of more help. do please post back though and let us know how you get on. take care:) Kabel. xx