Belly size / weight- opinions please

Lex
Hello,
I've always been overweight... Im 5'5" and I started this pregnancy (my 1st) at 188lbs. Im currently 17wks and I have a very noticeable belly. I've been wearing maternity clothes for like 3 weeks already. People keep commenting on the size of my belly and if I'm having twins. My family also makes remarks on my size. I don't feel huge but when I do look in the mirror I'm taken back by my size. I've only gained 7lbs so far but doc said I shouldn't gain anything else throughout he whole pregnancy. Is this even possible? He told me to hold out even if I'm hungry and to exercise a lot so I don't gain anything. I feel so depressed :(