Being a new mom wanting to go back to work or even school?!

I'm a new mommy, my son will be 3 months in a week. Before I had him I was sure I would be able to get back into the job field by now but I was so wrong. My son is colic. He cries all day, all night, and doesn't sleep for more than 3hrs at a time. It's very hard. My bf and I take shifts so we can both get some sleep but he's now looking at a big promotion that he can't mess up. I've been getting fed up though, before I met him I was so independent, working 6 days a week up to almost 16hrs a day. It seems crazy but I liked it and I loved making my own money. I worked on and off from the beginning of my pregnancy up to 8 months but nothing good because I was extremely sick all the time and couldn't eat anything but Ensure to help give the baby something. So my work life has been nothing like it was for a little over a year now. I want to go to school bad, and I want to start working again badly but my bf can't afford to lose anymore sleep than he already is with this promotion on the line, and I'm afraid I won't be able to do it on my own. I know there's people who have newborns/babies and work or go to school but I would really like some advice or freedback from parents who've gone through it & accomplished it.