Hi!
I got married in and since then we are enjoying sex, We did not use any precaution during sex as it lessens the pleasure. We were not in a hurry for our first issue, So as a precaution what I use to do is, when I was about to I use to (ejaculate) outside. As such my wife is missing her periods, So I am worried whether she is pregnant. So my question is, is she pregnant? How can she conceive when I use to (ejaculate) outside ? Are there any other reason for missing or postponement of periods ?

"pulling out" does not stop pregnancy, it merely lowers the amount of sperm, There are still plenty of sperm in the early fluids for pregnancy. Pulling out will lower the odds but people who just pull out, will become parents at some point.

Even though married, you really need to educate yourself on sex, pregnancy prevention if you do not want to have a child.