D., you definitely do sound torn between two decisions. I don't think any kind of work replaces the work you do at home as a SAHM. But that's just my opinion. Before I had children, I was in the corporate world, but boy did my priorites change once I had kids. My husband and I both talked about me quitting work once we started having kids, no matter how hard financially it can be.
I read once, 'we don't have children with money, we have children with faith.' If money is one of the reasons, I wouldn't go back to work for that reason.
If it's because you are feeling lonely as an adult because you are just around your little during the day...that will pass as you get together with play groups and as he gets older so you can cart him off to this and that type of place to explore and educate him more on the wonderful world that we live in. You'll get to see his enjoyment learning. And as additional children come along, it certainly won't get lonely.
I remember you saying a while back that you'll be starting school again soon...that will probably help out in many ways for you before you guys start having more children. More children will definitely keep you busy and challenged.
Good luck D. on your decision, but remember, as a unit, you and your husband would definitely need to agree so it won't cause additional problems in the marriage.