My monthly cycle is 28 days,my last period was on the 20th of January,I had unprotected sex on the 25th, followed by a brown discharge 2 days later,and for the past few days I've had period pains.I now have a white /clear discharge... I am 33 and have one child who is now 15??

You risk pregnancy every time you have sex, protected or unprotected. Only time will tell - or at least enough time has to pass in order for you to be tested.

I did check and I don't think I was due to ovulate till the 31st , my chance of pregnancy could be very slim? I hope as I am normally very careful?

You took a chance - ovulation varies from month to month.

Only time will tell.

You checked ovulation by using body temp? Only way to check, online or phone apps are just silly jokes, since all women do not follow a day number in ovulation