What Are The Side Effects Of Having An IUD?

I have a question about my period before when I was younger I had got pregnant and I had the baby and I decided to get the IUD (intrauterine device). I kept IUD in for five years and I got it taken out, for that five years I did not have a period at all. And before I got on the IUD I was on the birth-control patch for three years and I had a period Every 28 to 29 days and I only would bleed for three-five days but it was always a very light period. But now that IUD has been out for two years and I have a period but it is extremely light I could wear my pad for all four days, that s how light it is. And mostly my periods are like a brown color, like old blood. Now I am over weight, I have recently lost 30 pounds and I do see a difference in my periods. There s a little more blood than before but still not enough as in when I had them before. I ve been trying to get pregnant but no luck. I went to the doctor, they sent me to get a scope and did check my normal levels, she said everything came back fine. I m just scared that that IUD did something to my body.