Implantation spotting and cramps 4-5dpo

Sorry TMI- I had a very tiny bit of yellow clear cm with few barely noticeable drops of blood yesterday. Today also my CM was kinda off-white with a few strings of blood that looked even rusty in color but it was a very small amount. This usually happens only before AF which is due in 9 days. And btw I had an HSG last Monday. Im confused whether this could be IB or some infection from the test even though there is no smell or burning or anything. Or I am thinking it might be some cyst that ruptured (i have Nabothian cysts on my cervix) but I am not sure if it would look like this. I know IB usually is between 6-12 dpo but I heard of cases where it happened as early as 3-5 dpo. Thank you for reading and participating in my Poll.