I am surprised that your OB/GYN told you that you could have endometriosis because of the spotting and mild pain! Both of these symptoms are very typical of ovulation! Some women don't know or have any signs of ovulation but some do and spotting and mild pain include them. I always had the mild pain during ovulation and will also switch sides from left to right, depending on which side the egg is being released from that month.
Also keep in mind that you came off your BC not too long ago so your body is still adjusting and you could spot at other times during the month too which is all normal.
At this point I don't think you should worry too much unless the pain is really bad e.g. I have PCOS and used to get cysts on my ovaries. At the time I did not know it but the pain was bad and with every step I took it would ache and it was on the side that the cyst was. If you do get pain that bad then you should definitely see your doctor.
I found the book "Taking Charge of Your Fertility" extremely helpful, it teaches us women things about our bodies which no one usually tells us and covers everything from preventing to getting pregnant, PCOS, endometriosis, menopause, etc. You can find a gently used copy at Half Price Books.
Good Luck!