Upload issue with streaming services

For the past two months, I have been having an uploading issue with trying to stream to Twitch.tv. It started in early August and at first thought the problem was with Twitch's ingest server. However, after weeks of this issue I made a call into Cox Support. They performed some test and noticed some packet loss on my end. They sent out a tech and he replaced the cabling in my apartment from the modem to the outside box. He also check the connection at the pole and was unable to resolve the issue. At the time, I was using my own modem/router which was recommended from Cox website. Cox Support at that time stated that the issue was with my modem and I would have to replace it with one of their own in order to get further support. Skip forward two weeks after a shipping debacle and BS. I just got the new modem installed on Tuesday morning an the issue is still there. I am at witts end on this. I have also tried streaming to Hitbox.tv and Youtube Gaming. I get the same issue. I have reduced the upload bitrate of the software to 500 kbps and I still get problems on the stream. I'm using the 100 Mbps down, 10 Mbps up tier. Can I please get some assistance with this issue?