Could it of been ib.

Ok so my last period was on April 17th. It lasted about 4 days. We had sex after this and on the 30th we had sex. The next day i had some pinkish/brown spotting when i wiped all day and then it stopped. Could this of been inplantation bleeding? My periods are sometimes late but its predicting i should start on the 15th. Weve been trying for our 2cnd for almost 3 years now.