Can you inplant at 4 or 5 dpo

Hello I have 2 little girls and have been trying for number 3 for about 6 month. I had a positive opk on the 4th and 5th of may which turned negative on the 6th. I had intercourse on the 4th, an light pink heavier than spotting but lighter than a period when i wipe and cramping only on the 8th. My cervix was low and closed on the 6th through 8th and is now high but still closed. Im not due for my cycle till the 18th or 19th and wanted to know if that could have been implantion bleeding?