I am 20 years old and have been regular until now. My cycles normally are 28 days, seldom sometimes 1 or 2 days late or early. My period generally lasts 4 days. I just finished very short, light and early period. Before that the last cycle was 27 days. This one started 23 days after the first day of the last. So 4 or 5 days early depending on how you look at it. It started in the morning (after having sex the night before) and lasted for 3 days. It was a bit lighter than usual. Day 1 was very light getting bit more towards the evening Day 2 was close to normal, albeit a bit light but enough that I had to change tampon once Day 3 was light again and it stopped late in the evening On the last day of period I had some headaches. Another headache the day after and again today. I also had a little bit of nausea on the last day of the period but not today or any other day. No other strange signs. About 2 months ago I started having sex. I have always used precautions (condom) and have been very extremely careful. During the last cycle I had sex 3 times. I am very worried this may be implementation bleeding. Like I said, I have been VERY careful, the condom did not break and he did not come inside of me. This also corresponds with exam stress and as I mentioned, I only recently started having sex which may have led to some hormonal changes. Is this likely to be a weird early period, is there a large possibility that this may be implementation bleeding or could there be any other explanations for this?