18weeks pregnant I need some advise

Deminica • I'm a newly soon to be mummy to a gorgeous boy in November 😍😍
I've been told I'm underweight for my pregnancy and I was wondering if anyone knows a good way to put on more weight I have to try to gain 5-7kilos :/ but it's hard for me I've tried but all I gain is 0.1 each time and I'm worried. It's my first pregnancy and I've lost a baby before...please help me ❤️