Combining ethernet ports is covered here Combining two ethernet ports. Unless you have link aggregation enabled, your OS is likely just using one of the ports. Also, you are most likely limited by the WAN connection in your instance.
You didn't mention what kind of WAN connection you have (e.g. DSL, FIoS, cable, etc.) or the speed of your ethernet connections, but it is most likely that your PC's networks connections (100Mbit? 1Gbit?) are both much faster than what your WAN connection (1Mbit?), so aggregating the two won't really buy you any better speed.