At my first appt I was 7w5d and had gained 4 lbs. So I'm sure you're fine. :)
I'm 18+4 weeks and have already gained 16 pounds. You're perfectly fine!
If you're eating more than 300 extra calories (in addition to your normal daily caloric requirements), you're eating too much.
Every pregnancy is different hun. My first appt I had gained 15lbs from my pre preg weight! Then it slowed down to only 2lbs. As long as you're not losing weight and your Dr isn't concerned you will be fine
You'll be fine, by the time I was 12 weeks I had already gained 8-9lbs, haven't gained any since though and I'm almost 16 weeks. (: If you're concerned about it, try snaking on fruits and veggies.