After 5 yrs with Mirena, got it removed, now have long scanty periods

I had periods that were heavy, 7 days, and without birth control 19 to 90 days apart. I got Mirena and stopped having periods. I got it removed after five years, and since then my periods are 30 to 36 days apart, and 11 to 13 days long. But they are so scant I bleed lightly one or two days, then light spotting the rest of the period. I mean spot so lightly that even though I'm wearing a pantiliner I never get blood on it. I'm afraid that means I'm not building up enough lining in my uterus for a fertilized egg. Has this happened to anyone else after Mirena? I am 35 and have PCOS, hypothyroidism, and other medical issues.