How to know when its worth calling the doctor and when its not?

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My doc is cautious, call at any sign of blood for example. Well, I called once and she basically said its no big deal! So now, after going to the bathroom (no. 2 sorry if its TMI), I saw blood again... this time more than I saw a few weeks ago! I am 34 weeks. I dont know where it came from? It wasnt that much but it was enough and bright enough that I sure wouldnt consider it pink-spotting!

Im so confused about when to call and when not to. According to them pretty much everything is normal. When I had my son 9 years ago, I was induced and the whole pregnancy and labor was so easy. This pregnancy has been the opposite so Im freaking out. Would if labor signs are there and I blow it off assuming its "normal" until its too late?