Hey Im A 24 Year Old An I Had The

Hey im a 24 year old an i had the inplant in an my last period was 1/10/2016 i ovulated on 1/23-24/2016. I had some bleeding on the 2 and spotted the 3&4th light pinkish color blood the 3-4th not the 2nd ot was red how im pregnant how can i know and let my ob know that this baby os a planed baby when he said my last period was 2/14/2016 but i never had a period in February and this will be my 3rd son