Yes Avocado and milk helps :) Durians helps too 😉 ( I had durians on my 2nd trim ) 
Maybe you can try. 
If youve blender at hm , you can do homemade Avocado milk shake, banana milk shake etc , spread Peanut butter and bread , meat , Fatty fish (like salmon), eggs , cheese , ( don’t forget vegetables too ) etc and u can snacks in between. 
U will see difference on 2nd trim onwards. Every bump is different, don’t stress 😇 
My SIL is very petite , she had a small bump  when she was preggy 😁 
If you are worry, you can talk to gynae, ask for a list how to gain weight. If your gynae noticed u been putting too much weight by then she will ask u to stop eating alot lol. Is also ok if u don’t put much weight thruout whole preg. As long baby is growing well ;) 
I put on abt 8-9kg during my 10m pregnancy , I just eat normal 2-3 meals. I don’t eat snacks much or eat supper. But occasionally I had sweet desserts n durians  etc 
On 3rd trim it shoot up a little fast for me , I stopped eating durians . 😅
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