how long to test after IB

so I'm starting to think I got my hopes up for nothing. last week I had some very slight cramping and so tired. well on Thursday I had literally one drop of blood. I thought I was maybe starting early but after that one tiny drop of blood nothing else came. well the last 3 days since I had what I thought was possibly and hopefully IB I have had nothing but BFN tests. am I testing too soon. how long did you wait to test before you had your BFP. the other problem is I have pcos so I'm very irregular and have no idea when I ovulated and when my next period will be. last month my cycle was 37 days. am I getting my hopes up for nothing? every passing month gets harder and more hopeless. I'm praying I just am testing too soon but I don't want to get my hopes up for nothing. although I guess it's too late for that. lol