Hello welcome to health care magic, I really appreciate your concern. since you had unprotected sex so I would advise you to rule out pregnancy first by doing urine pregnancy card test which can be done at home with first voided sample of urine because blood clots in Menstrual bleeding might be related to product of conception. Blood clot with whitish colur and heavy bleeding in the backdrop of lower abdominal pain might be Infection or inflammation of the urogenital tract or PID (pelvic inflammatory disease). In my opinion you should visit a gynaecologist immediately for baseline investigation not only the assess the extent of blood loss but also to find out underlying cause which could be a missed abortion, infection or hormonal imbalances. Meanwhile maintain good hygiene and drink plenty of fluids to maintain good urine output which will help by flushing of the urogenital tract. You may require iron and multivitamin supplements to replace the blood loss during the heavy periods. you should also take antiacidity medicines like pantoprazole or ranitidine for symptomatic relief from Acid reflux. Hope this answers your question, please feel free to ask for follow up question. Best wishes