I'm going crazy

My period returned about a year ago after my son's first birthday (breastfed, so took 13 months to return). I don't feel like my period is coming and I'm currently 4 days late and getting a BFN. I went through my tracking from the last year and saw that there has never been more than 5 weeks between periods (actually the longest time between them was exactly 5 weeks and that was only once, right after it came back) with average cycle length of 33 days. Right now I'm at 5 weeks 1 day... I just want my BFP!!! I'm 35, and if we don't conceive by the end of the year, due to my health issues, I think my doctor will advise against it, as she already told me that 35 was pushing it..... please tell me that I may still be pregnant but my body just doesn't have enough HCG to be picked up on a test yet....