You've probably already got tons of great advice but having been through this with both of my pregnancies I thought I'd share
With my first the doctors were just expecting me to get gestational diabetes because I was around 290 (5'10") but I never did... that was kind of annoying. I ended up eating so much better with my 2nd that I lost weight.
My words of wisdom... it is very common to feel fatigued constantly throughout the 1st trimester. Appetite usually spikes around the 2nd but as the baby gets bigger in the 3rd, your appetite goes way down.
I delivered 2 very healthy babies & found that staying active during pregnancy made for a smoother labor.
Best of luck to you & just remember that you are not the first big girl your doctor has seen and you wont be the last so don't be embarrassed.