I've had long and irregular cycles for the past couple of years. When my cycles were 45-60 days long, I was ovulating.. but when they went longer than that I don't think I was. I highly suggest watching your mucus closely, and once you notice a change in that, start using OPKs to tell you for sure if you're ovulating. That is how I knew each cycle. Also, since you've been having 50 day cycles, you should be ovulating around CD 36. Most women ovulate 14 days before their period starts.
I had a miscarriage in March, but the cycle I got pregnant would have been a 42 (I think) day cycle, so my cycle lengths were coming down. Then 7 weeks after my miscarriage I got my period, and now I'm in the TWW with a 30/31 day long cycle! Losing some weight has helped me a lot with my cycle lengths, but I'm not sure if that would help you. I also took some EPO this cycle, and I think that played a huge role in shortening my cycle lengths.
As for the implantation bleeding, I'm not sure. Just wait a couple of days and then test.