Hi,I had procted sex,but now its been 5 days having terrible headaches,pains in my stomach and backpains.. please what could be the problem

There can be 1000 reasons for this, you did not say what type of protection, if just condoms they can have a 3 to18 percent failure rate, so of course pregnancy can be a option.

Also how long has it been since you had sex ? Just 5 days, There would be no signs, since it takes the sperm about 3 days to reach the egg, Often the first sign is a missed period . Are you getting near your period due date ?

Yes I have been in my period already this month so my next date is on december_its been 5 days feeling this way(terrible headaches,pains in my stomach,backpains and my boobs itchy and hot..

I would go for a check up to be honest. None of this sounds like pregnancy. It could be but the only symptom that is reliable is a missed period.

5 days after sex is too early to have pregnancy symptoms.