Falling asleep at work ?

So im 10 weeks pregnant and I find it hard to stay awake towards the afternoon. I’m currently at work and it’s 230 and I am so sleepy. I already had my lunch break so I can’t go quickly nap. My manager isn’t in, I work behind a computer at my own cubicle. Do any of you pregnant ladies feel so tired at work? What do you do to stay awake. I have 2 more hours.