What could possibly be going on?

My boyfriend and i had unprotected sex using the (pull out) method a day after my last period. A week later i noticed some spotting, but only a little.. not lasting a day. Two weeks before my period i now notice the same brownish spotting. This is unusual to me. Ive researched what this could possibly , most results coming up with implanation. Other sites say that just after a period spotting is just cleaning out your system.