Missed 2 periods but negative HPT? 😁

I'm 17 and I'm 40 days late. I took a couple of hpt a week or two ago and they were both negative. Me and my bf don't use a condom, I'm not on BC, and he doesn't pull out and we've been having sex since October. BUT here's the thing. I stopped the pill in August and my periods have been late a lot since then, just not this late. I was 31 days late one time and I went to the doctor and I took a test and it was negative. Im just really confused and I don't want to go to the doctor again for nothing.