I feel constipated, but little strands are coming out. i've just taken some milk of magnesia (magnesium hydroxide). if it doesn't work, what should i do?

Don't strain: Whatever you do, do not strain as this can cause hemorrhoids. You feel constipated. In general you should have a bowel movement at least once a day. I would try at your age some basics like drinking more water, increasing fiber especially greens, and exercising. Mom is ok but you are forcing a bowel movement. If bowel movements continue to be a problem then see a gastroenterologist.