4 Days late and still bfn 😩

Ok so back story: 2 years ago I had my mirena removed and was ready to conceive baby #3. Well for about a year into it my periods were irregular and then I started having 33 cycle days. It’s very frustrating. My period was suppose to start on Christmas and nothing. With my last two pregnancies I got BFP the day after my period was due. Im so confused. Im not stressed in any way but I guess what I’m trying to ask is how long after af is due did some of you receive a BFP? If still nothing by next week I’m going to make a doc appointment.