I have lower abdomen pain. gets worse after intercourse and sometimes there's a bit of bright red blood. feeling nausea all the time. also have lower back pain?

It sounds like a pelvic infection, but there are many other possible reasons for this. See a gynecologist

Any abnormal bleeding warrants investigation. In your case a gynecologist would be the best type of doctor to evaluate you. Have a healthy diet, exercise 30 minutes/day, drink plenty of water daily so your urine is mostly colorless, have safe sex, no tobacco alcohol weed or street drugs. For nutrition: http://www.choosemyplate.gov/. Get HPV and Covid vaccines. Wish you good health!