pregnant?

What are your experiences with implantation bleeding?
I have been very lightly spotting brown and pink blood and I’m wondering if it’s a sign of pregnancy. 
I’m sexually active (same partner, my husband, for 10 months) and use the pill for birth control. I have had mild cramping and one morning I woke up with nausea. I have also been experiencing some constipation. No other symptoms. 
I’m waiting until the appropriate time to take a store pregnancy test and scheduling an appointment with my general doctor soon. 
Any advice or stories of your own experiences? Thanks in advance.