Well it would have been helpful if you had mentioned several other facts like the MCH, MCHC and the MCV which would have been reported. There are diseases where the iron is not incorporated into the hemoglobin and hence the iron levels maybe normal or high but the Hb may be low still. Thalassemia is one such disease but it manifests at an early age, like 5-6months of age, and hence don't fret about it.
Skyla is a small, flexible plastic T-shaped system that slowly releases a progestin hormone called levonorgestrel that is often used in birth control pills. Because Skyla releases levonorgestrel into your uterus, only small amounts of the hormone enter your blood.
According to the Skyla IUD - FDA prescribing information, side effects and uses table 1 (scroll downwards a lot to find the table) not having any periods nor spotting during the first 90 days is quite rare, less than 1%, but you had had some spotting, and your pregnancy test is negative. If in doubt, repeat your pregnancy test. If not pregnant, and you have not further symptoms, I wouldn't worry, levonorgestrel containing IUDs like Skyla can cause the abscence of a period (total amenorrhea meaning no spotting too) in 3% to 12% (the later after insertion the higher).