Overwhelming

I am a newly trained IT professional, just graduated in May. It seems however that every task I undertake is a little over my head. My first was not too difficult I set up a simple peer to peer LAN in a corporate facitliy. Second, a VPN solution between two geographic locations. Now, I may have bitten off more than I can chew. I will be designing and implementing the entire corporate IT infrastructure. Im not really sure where to start. Then entire project is in my hands and right now in my career they are pretty small.