Started birth control in sept, bled for 4 weeks. had sex in june but had my period in july and aug. is bleeding and stomach pains normal? test neg

Yes...: It is definitely possible to have abdominal upset and abnormal vaginal bleeding after starting new birth control hormone. However, if you had sex before starting it and having this type of symptoms I would recommend to have a pregnancy test done if you haven't had one.If negative, give time to the contraceptive to stabilize your hormonal system. If still with symptoms might need different one.