Late period

I am now 5 days late and my lower stomach just has this weird feeling and I know I obviously can’t be pregnant because i never had sex besides just make out with a guy last month around the end of April and last month I got my period on the 7th a Sunday and had it for a couple days and then a week later got it back so idk if that could be a reason I’m late right now or if it’s because I’ve been extremely stressed since then. I’ve been on birth control for over a year now and yeah I do mess up the times a lot when I take it and end up having to take two in one day bc I forget to take it. I just don’t know why my lower stomach feels so weird and my back and top of my legs yesterday were killing me and I’ve never had my legs hurt before like that. Please help me out here bc I’m worrying so bad that it could be something worse even though I obviously know I can’t be pregnant.