Weight/Avoiding gestational diabetes

So let's start by saying I'm over weight.. I'm 5'1 and 155 lbs. My question is my doctor told me he'd prefer me not to gain weight but if I must to only gain 10lbs, we're aiming to avoid gestational diabetes this time. So far I'm doing well but I'm only 11w5d. My question is anyone one else struggling to not gain? I check my weight once a week and I've gained nothing but I know second trimester is when it really hits and I'm worried that I won't be able to avoid gestational diabetes..