You can try to take fresh milk and milo, I have been taking fresh milk 1L per day (5 days a week) for 2 months, my boy now 34w2d now and he is 2.7kg.
This might give you some information. https://www.urmc.rochester.edu/encyclopedia/content.aspx?ContentTypeID=90&ContentID=P02411
try taking avocado or even durian.. can boost abit more weight for baby inside..