Im exporting a project im working on to pass to my buddy via dropbox, but the file is 72 mb. Im not sure why, Its no larger or more sophisticated than any other projects I normally send out, and those usually stay around 20 mb. I have an instance of omnisphere, two instances of absynth and one instance of battery 4. 4 tracks in total, haven't even begun mixing it, almost no processing, its just a rough draft. Now the project is about 7 minutes long, but most of my 20 mb projects tend to be around 4-5 minutes long and they never give me trouble.
 
any Ideas how I can significantly shrink file size? exporting to wav, signed 16 bit.. thanks!

It does not matter what is making the sound or if there is any sound at all, the size of a stereo WAV is the product of ((Sample Rate x Bit Depth) X 2 Channels for Stereo) x Runtime. If you want a smaller WAV you will need to adjust those values or export a different format (like FLAC). Exporting 16bit will reduce the size if previous exports were a higher bit depth.

Something's not right here.
If you really are talking about a normal stereo wav, then that 72 mb  sounds like a normal size (think about a CD) for an  "about seven minutes" -song. So ten of those songs would last about 70 minutes / about the duration and data size of a CD.
 If a five minutes long song is only 20 mb, as you say, it would mean your audio CD would last about 36 x 5 minutes = 3 hours, which is not possible.
Either you have been exporting at 22 kHz sample rate instead of 44,1 kHz, or you have exported to some other format instead of wav.