I just wanted to thank, from the bottom of my heart, every single person who replied with so much thought and sensitivity to this question. I am touched by your responses and you all have helped me immensely.
I have been a SAHM twice in my life. First, when my eldest two children were small. When they were 3 1/2 and 1 1/2, I got divorced and returned to the workforce. Then, I became a SAHM when my youngest child was born and I've been home with him for 3 years.
Bottom line: staying home FT doesn't work for me. I had an incredibly hard time making the decision to go back to school FT this fall and finish my degree, and I felt very guilty. Now, though, I'm getting so excited about being back at the university, and since I'm very close to finishing, I'm also excited at the prospects of bringing some money into this household.
My youngest started in a great day care near our house (I used to work there) about 2 months ago, so I've had time to work on some of the writing projects I've had knocking around in my head all this time, and it feels sooo good to do that.
Surprise, surprise, every single person in my family is happier now. The kids know I'm happier; I enjoy my time with them 1000% more than I used to because I'm not depressed, anxious, bored, and lonely.
As much difficulty as I had making this decision (I have definitely bought into some of the "SAHM is the only right way" rhetoric), I've always believed that the whole WOHM/SAHM debate is silly. It is every conscientious, loving parent's responsibility to make decisions for the family that are in every family member's best interests. There is no "best" decision for every family. There are only "best" decisions for each family. And if Mama ain't happy, ain't nobody happy!