I have abdominal pains in my left ovary, and even during sexual intercourse. is it something serious?

Hard to tell: It's hard to know if it is something serious - you should probably see a doctor and be evaluated. If it is on your left side, it is probably not your appendix. It could be your ovary, bowel, or even your muscles. It may be a muscle strain, ovarian cyst, infection, etc. Could be many things. You probably need an exam, and possibly a pelvic ultrasound.