Feeling guilty for leaving work..?

Brieanne • 26. Married. Baby G due Jan. 2016!! ❤️
So I had to leave work today because I felt like I was going to faint. I don't go home often, and I only knew for sure that it was a fainting feeling because I have fainted before (low blood sugar about 4 years ago. No fun) I was going back and forth between feeling faint and feeling like I was going to throw up. I made it home and fell asleep on my bathroom floor for like 4 hours. 
I guess I'm just wondering if anyone else has left work and how you felt about it? I feel terrible even though I keep telling myself I was useless there.