hello there.
If you had your periods this month and the bleeding was as heavy as your previous cycles, then
pregnancy is not a possibility. You had unprotected sex last month after which you have menstruated for 5 days. Besides you were taking OCP's also. This means that your sex was not unprotected in a way provided you were taking the pills regularly and did not miss any dose. Just wanted to know if this bleeding started after stopping the pill. If yes then there is no chance of pregnancy.
Bleeding which occurs after pregnancy is
implantation bleeding but is lighter and lesser than your periods.
Its mainly the anxiety due to unprotected sex you had which makes you think you are pregnant. To allay it, you can do a home urine pregnancy test for satisfaction.
Low back pain and cramps could be because you are in your mid cycle period where in ovulation takes place. Ovulation can present with these symptoms. The other possibility is genital infections especially if the
backache is associated with
vaginal discharge. In that case you have to get yourself internally examined by a gynecologist.
Remember, if you take your
oral contraceptive pills regularly at a fixed time, there is no chance of pregnancy even if you do not use a
barrier contraception at the time of intercourse.
take care