Hi Lisa -
I am a SAHM to my little guy and I would not trade it for the world! I, like you, went back and forth deciding what to do. I invested a lot of time and effort into my education and career (though not as much as you) and initially I didn't want to walk away. The day my son was born, there was no question in mind...I was staying home! I am so glad I made that choice, especially since my little guy had needed extra love and attention and had feeding issues, reflux etc. I always would have wondered if he was getting all he needed if my husband nad I were both working.
Don't get me worng, I don't think there is anything worng with working Moms at all...I give them a lot of credit. I also know that staying home full tiem is the best, but hardest job I have ever had. It is almost like you know too much about what is going on!! I have joined a few things, like Gymboree, and it is great for both he and I. He sees other kids/faces and I can chat with other Moms in person!
They do grow up so fast, so if you are able to stay home, by all means jump at the chance! You can always go back to work if you feel you made the wrong choice...or when your kids are in school!
Congrats and good luck.