Very faint line fading

Okay so took a test Wednesday evening.. very faint line and got a little darker after the 3 min window.. took a test Thursday morning.. very faint line again but visible and clearly had pink to it. Took these two tests Saturday morning back to back.. ones there with color (top) and one is like barely there (no color) and this morning I took one clear blue (negative) and another first response which was negative. Never had a chemical or miscarriage before and never had fading positives with my previous pregnancies? What do you ladies think? Also I’m 12 weeks postpartum. Don’t know if that has anything to do with it. I’m supposed to get my IUD placed Tuesday of course 🙄 so I’m planning on calling the doctor tomorrow morning and maybe get some bloodwork going.