Any ideas ?

ok so I had my last injection around June time and I haven't had a period but I know I've ovulated atleast twice since mid August. we had intercourse about 2 weeks ago and a few days ago . since yesterday I've had light brown dishcharge . today this continued but for a few hours there was a pink tinge mixed with the brown discharge I had slight cramps which have now gone. still have the brown discharge but all this is confusing as I had nothing with my little boy until later on .