pains/ funny period things

i've been really lazy the past few days and i got my period about 4 days ago so seriously when i'm at home i barely bleed and barely cramp at all but AS SOON AS I LEAVE HOME ITS NIAGRA FALLS AND CRAMP CITY. it's not a big deal just funny. if anyone has any idea why that happens please let me know. also sometimes when i'm on my period i get super intense shooting pains sometimes from my anus to where i get cramps (always the right side) and sometimes the pain goes from my stomach to my anus and just now it shot from just under my ribs to my anus. it goes away rather quickly. any answers on any part would be super helpful