Help please!!!

Hey ladies I’m really needing some insight. So a little back story here. I got my Mirena out December of last year. Got pregnant in February and unfortunately miscarried in April. We have been trying for our rainbow baby since the miscarriage. I have never ever had late periods unless I was pregnant. Well as of today I am 4 weeks late and have officially missed two periods in a row. And hpts have been negative. Got my blood drawn once and it was negative also. I have been gaining weight, slight nausea, and my boobs are somewhat swollen. I am just wondering if anyone has had anything like this happen and end up pregnant but tests were saying negative? I’m planning to call my dr next week to request an ultrasound. Any insight or experiences would be great. Thanks!!!