What Causes A Heavy Period With Pelvic Pain?

i have took 8 pregnancy test for positive 4 negative i have done research and you can have false negatives and false positives. but i have pains i my back and lower right side stomach and pelvic area. i smoke and know its bad but it hard to stop so wat i wana know is it possible im pregnant is it possible im having a mischarage and i bleed for two days heavily nothing like a normal period