Sides hurt (like cramp feeling), and lately blurred vision and dizziness when i stand up...?

so sometimes, not very often, but sometimes my sides start to hurt, but if i sit down for abut 5 minutes it stops and usually doesn't come back for days, weeks, or even months. and lately, everytime i stand up i get dizzy and my eyes get blurry for about 5 seconds. and my head is constantly hurting , but very dull headache. what is this? i'm scared i have kidney failure, diabetes, high blood pressure or something. what is this? im scared. btw, i'm a 14 year old boy. my sides have done this for a long time, but it doesn't do it much. when my sides hurt, they feel cramped and it hurts to walk around until the pain stops.