BUT implantation takes at least 7 - 10 days, normally (a LP of less than 10 days is considered not long enough) and i think 14 day LP is average, so even if there was an egg ready, which fertilised (which normally happens several hours after sex) it is unlikely to be able to implant
Actually, it's not quite true that you are fertile at any point in your cycle.
There's an 'absolute infertile period' in which the risk of pregnancy is almost absolute zero from about 24 hours after ovulation until the end of the cycle.
But unless you know for a fact that ovulation happened, from charting or something, then the bleeding could have not been a technical (in family planning terms) period and just been bleeding. And if you have an anovulatory cycle (no ovulation) then you are fertile from day 1 of the next cycle; so it's possible that you might be pregnant from it if that happened and if you ovulated right after the bleeding as sperm can survive for about 5 days in favourable conditions
TBH I wouldn't have thought so, not if it was just before your period would normally have been due, then your period arrived on time and was normal length/heaviness etc. Because your nomal period just after would indicate you had ov'd at normal time 10 - 14 days (ish) before.