I have a sharp pain on my lower left side of my tummy. hurts a lot but mainly when i have to pain but it doesn't burn. do yu know what it cld be?

Many possibilities: Common causes of sharp pain in the left lower abdomen in an 18 yr old woman: ovarian cyst, mittleschmerz (pain from ovulation), ectopic pregnancy (of great concern if a home pregnancy test is positive), std (infection or pelvic inflammatory disease), colitis, kidney stone, abdominal muscle strain, hernia, ovarian torsion (though this is usually sudden and severe). Needs evaluation (& preg test).