FPGA Power measurement
The standard way to check power being drawn by a component on a PC board in a system is to open up the DC power paths to the FPGA and then insert a known resistance resistor in series between the FPGA and its power source. You then measure the voltage drop across this resistor through two wires that you connect on each side of the resistor and bring out of the system to a current meter. Two things to consider, the resistor value has to be really low in the less than 100 milliohm range so that the resulting voltage drop does not put the FPGA into an invalid operating scenario.  You also need to carefully consider the wattage rating of the resistor used so it does not burn or change values due to heating.

If you have access to advanced test equipment there are clamp on probes that can measure current in a conductor. If you have that then you can simply replace the series resistor as described above with a short loop of wire. Then clip on the probe. I've used probes that are able to measure DC as well as AC current.