Training energy question

stv1520

I've hired a personal trainer, who has developed a HIT (high intensity training) program. I've done 3 hour long sessions so far, and love the results so far. However, one thing has me a little perplexed: during these training sessions, there have been a couple occasions where I have felt lightheaded, and felt like I was going to pass out. I had to rest longer than I should, and my trainer wants me to get going! Afterward, I'm truly EXHAUSTED. MFP had me on 2,580 cal's, but my trainer upped me to 3000. I also play hockey 2-3 times a week. I'm wondering if I'm not consuming enough cals before these workout, or if I should be doing something different. Any ideas?