Mining Ravencoin, could use some help!

So I’ve been mining Ravencoin using my gaming pc and 2 GPUs (gtx 1060 6gb) for over a week now and everything has been working fine. I’ve been enjoying doing this so much that I bought two more GPUs, but my motherboard doesn’t seem to allow for more than 2 GPUs (MO: MSI X470 Gaming Plus Max).

I purchased a PCIe riser to use in one of the three PCIe slots but that doesn’t work either. Now I’ve heard about PCIe splitters, would this perhaps work? Or am I screwed and do I need to purchase a different motherboard?

Any help would be greatly appreciated!