Can you find a happy compromise?? Can you do work for an agency, flexible hours?
I had to go back to work p/t when dd was 3 months for financial reasons, I felt upset about this as i had always dreamed of being the perfect sahm. Instead i was this exhausted mad woman switching between professional and sensible, to this mad nappy changing, raspberry blowing creature.
DD is now 2 and i am very comfortable with the situation and wouldn't want it any other way. Now me and dd have got used to our routine i think it suits us both. She is very sociable and confident, and i keep my sanity by having grown up conversations at work.
How old is your son now? I think it took me a good few months to get settled with the idea. If your son is still v young, your emotions will be all over the place, and if you're anything like me you'll feel like your floating in fairyland most of the time. Give it a few more months and things will return to normality and you'll be able to think clearer about the situation.