Is it normal to p out after eating?

I've been trying to gain weight, so I've been eating healthy (veggies and such) and I've been eating a lot more. It seems like everytime I eat something though, I p out and wake up with a headache. It's been about a month since I stopped drinking energy drinks and coffee regularly, and I've been getting more exorcise working 2 jobs. I'm worried I could be diabetic, might have gotten Mono from a girl i made out with, or could it just be from eating so much? I've only really gained maybe 10lbs in the last month. I weigh about 120lbs.