Pregnancy possibilities. Any difference?

Is it possible for me to get pregnant if I'm on regular combined contraceptive pills and take them without missing any doses at the same time each night. Me and my husband also follow the withdrawal method as an added precaution. Does that make any difference? Recently, there has been a buzz about stealth pregnancies which made me take blood pregnancy tests, which were negative and upts which were also negative. Also, I've never missed a period or even had extremely light periods since I started ovral-l. I get regular periods with cramps and moderate bleeding for 5 days each month. Should I worry at all about stealth Pregnancy or relax. P.S. I had a transabdominal ultrasound in June which showed no gestational sac but I had 2 paraovarian cysts present. Do advise. Thank you.