Congrats on being able to stay home that long with your baby, I am not going to sugarcoat it and tell you it is easy because it is not, it does get easier with time. I had to go back to work at 12 weeks, so I know how you feel, I was very lucky that I was in the same building as her when she was real little. I was able to go see her when I needed some reassurance. She did extremly well, they always seem to do better than us, she is now 4 and she loves going to her "school" and playing with her friends. There are many days that I wish I could stay home, but that is just not in the cards for me right now.
Good Luck, just make sure that you are happy with the child care that you are putting him into and trust your instinct, it will get easier. :)