Long implantation bleeding??

Advice please. (Sorry if TMI)

Last actual period was 11th-14th sept..was supposed to come on on roughly the 19th october, however period didnt arrive. Myself & my fiance are ttc so lots of BD. On the 15th november i started with brown 'bleeding' which lasted until the 19th/20th november. It was on and off, sometimes pink sometimes brown but mainly brown and was very light (but not spotting). My periods are usually extremely heavy (soaking through tampon/pad in a couple of hours) so I have never experienced 'bleeding' like this before. Does this seem like implantation bleeding? I took a test on the 24th nov and it was bfn. Anyone have any advice or suggestions as to what this could be?

Thanks in advance