what fundamental did I miss?

I still consider myself a new trader (eventhough I have been doing it for a year) so prepare yourself for a DUMB question.

I recently started shorting stocks. My latest one was chevron.
I started my position when Oil was at about 130$ per barrel so in the beginings of march, My logic behind it was the OPEC agreement allowing a influx of Oil into the US causing an increase of supply lowering the price of Oil per barrel which in term will cause the stock to fall.
I was partially right, the review of the agreement happen and now about a month and a half later the barrel is at about $105 per barrel. HOWEVER Chevron kept rising and rising. I was able to be disciplined and set my stop losses and stick to them but I wonder.
What did I do wrong? I have to have missed a fundamental, did I enter too early on the trade? Was the reaction of the market going to take longer? Was my assumption of a lower price per barrel equal a lower stock share a mistake? I just want to know what did I miss?

TL,DR: I predicted a decreased on price per barrel and correlated it to the price of chevron, eventhough oil kept going down chevron kept going up. What did I miss?