No period but cramping?

So my period was due on the 19th of November but it still hasn't come, im 8 days late and starting to worry now. Ive had the cramps almost 2 weeks now as i usually get them up to a week before im due. Ive only ever been late once but came on exactly a week after. My last period was on 22nd - 28th October and had with my bf of 5 years about a week later. I feel like im gonna come on any second and it feels like Ive started bleeding and i run to the loo to check and nothing just a slight discharge (sometimes clear or white) I don't think i can get pregnant as im quite overweight (8st) and Ive smoked and took cannabis for almost 10 years. I don't have sore or anything and i havent had any stress. Im really scared to take a pregnancy test. Im also 23 I also havent been on any birth control since i was 16,my periods have always been regular as clockwork give or take a couple of days. Has anyone experienced anything like this before or have any ideas? Thanks in advance