Can I measure the current (mA) of my project with just a multi meter?
No, you won't get the right result measuring resistance. Integrated circuits contain lots of semiconductors which are inherently non-linear. 

You need to somehow put your multimeter in series with the power supply, set to the mA range. The easiest way I can think of is to use an external battery (7v or higher) and make up a custom cable with standard barrel jacks. As your board appears to have a linear voltage regulator, the current measured will be very close to the current consumed when powered from the USB port.