I fasted last yr when I was in my 4th mth. My own Muslim gynae did advise me against it as I'm prone to migraines, esp when I'm dehydrated. But alhamdulillah, I managed to fast for almost the whole mth. I ate a high protein meal with kurma milk for sahur to keep me full longer. For buka, I ate more carbs as they make me full faster. Of course veges and fruits for every meal and drink as much water as possible between buka and sahur. Of coz I had to wake up to go to the toilet often at night but tt time it was ok as I cld sneak in some naps in the day. It was during CB so WFH was a blessing. There were days tho when I had giddy spells and felt nauseous so I didn't fast.
But now, if u're still working as usual in the day, pls don't push urself too hard. Maybe try for alternate days and wkends instead. Monitor ur baby's kicks too if can.