I add my period January 5th to January 10th and I ovulated January 13th-18th and had unprotected sex with my husband and for the last week I started with back and side pain and just recently I started urinating more today I have been tired all day and have been feeling lightheaded and I am 3 days late getting my 2nd period for the month I am supposed to have my period on the 5th and 25th of every month and I am late does this mean that I am pregnant

It is rare, and really unusual unless controlled by birth control pills for periods to be exactly on a day. There are 28 days in some months, and 31 days in another, so just because of the 3 day difference, a period would never always be on the "5'th but counted by number of days between period.

Also the time from the 25th, to the 5th is from 8 to 11 days, not the time for another period.

Also the question, how do you know when you were ovulating, are you using basal temp readings, or other testing ?

You will need to wait for about 4 weeks to 5 weeks from the date of sex, to test for pregnancy. Also it is way , (way) to early for pregnancy signs.