M.P.
If you missed a day or took the pills at irregular times you can ovulate.
Pain in the lower abdomen and rectum is caused more often by several different things, including a digestive upset. You needn't feel sick to have your guts protesting against something you've eaten. I have IBS, irritable bowel syndrome and had those symptoms regularly. IBS usually starts as A. adult. I've also had that sort of pain after intercourse.
Our bodies are constantly changing which could account for the pain now that is not due to ovulating.
You can take a pregnancy test but do not stop taking the pill until you know that you are pregnant. You may, probably aren't, and you don't want to become pregnant. The pill will not hurt the fetus at this point. Most women do not know they're pregnant for another month.