What Causes Abnormal Menstruation?

Hi Dr. I am 26 y/o non smoker overweight 90kgs 156cm. Almost everytime I have a solid poop I get my period (quite a light flow) it may be like spotting or it can last upto 4 days. I also have gotten my period after a night of drinking alcohol and strangely after applying pressure to lower abdomin, my husband would rub my tummy with abit of pressure when I got cramps and i would get my period. I also get my usual menstrual cycle and can have upto 3 periods a month. I am on contraceptive medication which is the jadelle implant in my arm (3rd year now)...do you think this is the cause of these bizzare periods or would you recommend I have a cervical smear? Love to hear your advice before I pay $60+ to see my local GP. Thank you.