Running 3 External monitors from a Macbook Pro Retina 13" Mid 2014 I currently own a Macbook pro (Retina 13",mid 2014)
2.6GHz Intel Core i5
8GB 1600 Mhz DDR3
Intel Iris 1536 mb

3 x 22" Samsung Monitors. 2 of them running through Thunderbolt to DVI-D adapter.

The 3 monitor i have tried using both a DVI-D to HDMI convertor and USB to DVI convertor.

But i just can't get the 3rd monitor to run.  Any thoughts?? Is my specs not enough to run all the monitors?

Thanks
It looks like your computer can only drive up to two external displays (officially, at least). https://support.apple.com/kb/SP703?locale=en_US