the so-called contact bleeding your having during/after interourse has nothing to do with the pill. The bleeding is most likely coming from the cervix
- which can be quite vulnerable and might bleed when the penis rubs against it during intercourse. This usually is nothing - as many women have an "ectopy" of the cervix. This can be explained by describing it as an outward fold of the inner cervical canal which has many small blood vessels, seen in many women. However it can be caused by changes to the cervical cells - so it`s important to get a PAP Test just to make sure - there is nothing else that has to be treated. If it`s just an ectopy then you can have it treated locally - with ice or a solution - these close up the vessles that tend to bleed. This should stop the problem but it might return after a year or so.
So don`t change the pill, don`t worry but get a pap and let a doctor have a look (The doctor can provoke a bleeding with a small swab and see where it`s coming from. t`s also good to get a scan to make sure the bleeding isn`t coming from further up (which I shouldn`t imagine)