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If you have been on Microgynon 30 regularly and have a well-protected sex without any tear or spill, then there is no chance of pregnancy. Also when you are very sure that he did not ejaculate into you. Even though he did not ejaculate into you, his seminal secretions may have come in contact with your vagina, so also any infections lodged in his penis. You being so young, your vaginal and cervical cell lining will be very friable. They are very sensitive to tear and any infection. This can cause vaginal infection.
Vaginal infection, which is transmitted during sex (so partner is the source), so both have to be treated at a time or else you will get infected next time of sex. You may have white or yellow or grayish discharge with or without itching, foul smell, pain at beginning of sex due to dryness (as the lubrication will be reduced) and late towards the end, when fully erect penis touches the innermost vagina (due to inflammation of the structures around the uterus) pain radiating to the back or thighs. Associated to infection bowel movement is affected, also features of gastritis. Bleeding of periods will be thicker, darker, clots or fleshy masses like, may smell bad, more days with spotting after the periods too. When you have an infection inside the uterus, the blood flow increases as inner lining is inflamed and the blood mixed with the inner lining of uterus forms a thick, doughy or fleshy mass. As the healing of the lining is not complete, it keeps spotting or you have blood stained discharge. May have associated gastritis features like belching, constipation or loose stools, pain in lower abdomen, as the muscles and ligaments around uterus, are being irritated by the infection. You may not have all the features, but they may appear over time.
Pain is throbbing even before periods and last after periods are over too. Usually, infection is mixed and not just due to yeast fungus, there will be a family of aerobic and anaerobic bacteria, all of which cannot be detected on culture. When one is treated and cleared, other will grow and if not fully treated, it will regrow. Before treatment, confirm that you are not pregnant by having a home urine pregnancy test. You and your partner can have tablet Fluconazole 150 mg stat (only one tablet, no repetition), after lunch, tablet Azithromycin 1 gm stat (only one tablet, no repetition) one hour before food. Tablet Secnidazole forte two tablets stat (no repetition) after dinner. All these on same day by both of you. Later, you have capsule Doxycycline 100 mg twice a day for one week. Vaginal wash with V Wash or similar cleanser twice a day and vaginal pessary. Capsule Clingen forte or Candid-CL or Cansoft CL once at night for five nights. Your partner can have a local application of any antibiotic and antifungal cream. Candid B or Candiderma or Lobate GM on penis twice a day after wash for seven days. Do not have sex till the infection is fully gone. Do treat it as delay may send the infection inwards and may affect both you and partner's future fertility.