Hey. I'm hoping someone can help me...

I'm on the mini pill cerelle, and have been for years, although I had a 2 year break whilst having my 2 kids. Been back on it now about 6 months, but I've started to bleed, not much... First was last Saturday after I'd had sex... But it was brown, smelly discharge and lasted until the weds. Had sex again on sat night and had bright red blood when I went for to the toilet not much and some stringy clots... Today again when I went to the toilet there was a big red clot. I'm worried because I never had periods when I was on cerelle before, I've also had a weird feeling in my pelvis area... Not like period cramps... And my lower bad is a really aching. I've been to the doctors and they say no uti or preggers but have sent off swabs... I'm worried it's cervical cancer.