Going back to work early

Chelsea • I am 30 years old and have been dealing with PCOS my whole life.
So I live in Canada where we are blessed to be able to take up to one year off of work with partial payment. (Maxes out at $524 a week). My son was born May 30 so I'm not due back until June 1st but am considering going back to work 6 months early on December 1. Partly because of financial strain on my family, partly because I was on a career path and feel if I stay away too long it will get derailed and partly because while I love my son more than anything I'm finding myself falling into a slight depression being at home all day with 3 kids aged 13, 6, and almost 3 months. Maybe once the other two are back in school I will feel less stuck at home but who knows. 
I'm wondering if there are any other Canadian moms who made the house to go back early?! I'm worried I will feel selfish, I'm worried that I will miss out on those milestones. I'm also worried that if I stay home the full year I will put more strain on my family and stall out my career. 
We are also trying to conceive again right away as I have PCOS and it took us 15 months to conceive our son. So I worry if I don't go back we won't have the money for me to take time off again and maintain our lifestyle. Please don't judge. We absolutely can  afford to have our children it's just the longer I stay home the longer it will take us to get back on track with RESP and RRSP savings etc.