I ended a course of antibiotics on the 2nd April it was a 5 day course for a uti I can't remember entirely but may have been trimethoprim I was on. I completely spaced and on fri 8th and as I normally never use a condom with my partner I just didn't think and we had sex without one late on the Friday night/ early Saturday morning. I am on the microgynon pill but I've heard you're supposed to use extra precautions for a week after and the sex I had was 5/6 days after my antibiotics ended. I take my pill every day without fail, have been on it for 5 years and am only ever late taking it by an hour at the most when I do take it late. I was due on my period around this Tuesday 12th April and I have bled from then but it is so much lighter than I usually bleed only filling around a pad a day when usually I'd feel 2/3 for the first 2 days. It has also ended today Saturday 16th so that's only 4 days when I usually last 5. The blood is bright red and did have a flow to it but it was very intermittent and very light for me. So my question is could this be implantation bleeding that I have read about? I'm naturally very paranoid and have been stressed lately so I'd like some advice on how likely it is. I'm going to take a preg test around when I'm next due anyway and again after to be certain but in the mean time I'd like some opinions.