How can I tell if I am going in to labor?

I am 36 weeks and 3 days pregnant. I had my weekly check up today and felt fine after until about 2 hours ago or so. I have been having on and off cramps and when I recently went to the bathroom and wiped there was some pink blood on the toilet paper. The doctor did check my cervix but that was around 12:30pm and it's now 6:36pm here. She couldn't get to my cervix because of the position of my baby's head she couldn't quite get to it. She said my baby's head is really low. ( my bladder already knows this. haha) Well I have been having tightening in my stomach on and off every few minutes or so. It comes and goes but doesn't fully go away. My whole stomach gets rock hard it's somewhat painful but not really. I was induced with my first pregnancy and the contractions for me weren't bad at all and I barely felt them so this is why I am asking. The baby is still moving. She's always moving it seems. Should I give the doctor a call? Do you think this is just braxton hicks? I was laying down when it all first started and then got up to go to the rest room and do some dishes and it still continued. The last one I felt was at 6:20pm and now it's 6:41pm. I just feel a bit crampy. Like not full cramps but crampy like I am about to start my period. Not painful, just uncomfortable. I don't know how to exactly describe everything I am feeling. There isn't any more blood that I could see. Would you call the doctor?