on and off bleeding

my normal periods are every 5ish weeks, i dont take any pills and always use comdoms. but the past few months my period have been all over the place and im forever bleeding. finished last week and started bleeding again just now. i did have sex last night and bleed a little bit onnthe comdom then today im bleeding. ive had std checks and smear test recently all good. i do suffer with ibs and alot of belly aches. its becomming annoying. anyone else experienced this or what i can do?i will go doctors but its takes weeks to het an appointment. i dont really want to go on contraception as blood clots run in my family and i dont do very well with hormones being added to my body !!!