Weight gain in the first trimester

This is my first pregnancy, and I'm 12 weeks 5days. So far I've gained 8.5 pounds, which I hear is a bit much. I've been eating a healthy diet, but find it hard to fit in a workout more then 2-3 times a week with the job I have. I'm in my feet 8+ hours a day and just don't have a lot of energy after my shifts. My Pre-pregnancy weight was about 107lbs. Just wanted to know if this is normal or not, because I read that in the first trimester the most you need to gain is 4 pounds. Thanks!