Fast ways to get rid of constipation?

Ok so I'm a really poor Uni student and have $0 and I'm sooooo constipated and it hurts! I've sat on the toilet for like 3 hours today and nothing 😭 any ways you can recommend for me to excrete this horribleness without buying anything? I also have my period so constipation cramps and period cramps mixed together are the freaking worst 😢😢 sorry if it's tmi but I need so advice haha