Opk was negative but i have been feeling pressure in my lower abdomen and it's kind of hard also a lot more pressure when having intercours?

This could be: a lot of things. Ovulation predictor kits are quite accurate; the symptoms you describe are not that suspicious for ovulation anyway. Pelvic pressure can be due to uterine problems (endometriosis, fibroids, pelvic inflammatory disease), bladder problems (infection, interstitial cystitis), bowel problems (irritable bowel syndrome), etc. Seek evaluation for your PCP or gynecologist. Good wishes:)