Did I O or not?


I have been using OPKs this cycle, first after my mc @ 12w1d. I don't normally use them but I figured since it's my first cycle it might be kind of wacky and hard to pinpoint O...so I started testing 4 days before predicted O according to the app and got not line. Kept testing everyday until I started to see a darker line, then tested twice a day. Every test got darker, but still not positive. At least I don't think it was. So I kept testing and yesterday the line looked lighter than the night before. My question is- did I ovulate the night before and the test just didn't catch it, or maybe I haven't actually ovulated yet? I'm so confused.