Feeling insecure..

My fiancé and I are both so sure I'm pregnant, I know throughout this pregnancy I will have to watch my weight. I am a big girl and I know pregnancy will make me gain more weight that I don't even need. I don't like sharing with anybody my weight as it has caused a lot of insecurities in the past, I have overcome them but just don't like discussing my weight, not even with my fiancé or mum. I'll probably even feel embarrassed to be weighed by the doctor at check ups :( I'm scared he'll lecture me about my weight or something. I weigh probably about 85kg but I have always had trouble losing weight and have decided that maybe god just made me the way I'm supposed to be. I am confident with myself and don't care about my weight in general, but with pregnancy knowing that I'll have to have my weight checked all the time scares me and will make me feel so low about myself like I did a few years ago :'( what would you do????