Empire line is the very devil for mimicking pregnancy especially if you are otherwise slim. I can imagine how doubly hurtful it is for you to hear this considering the circumstances.
How to flatter a curved tummy? More fitted clothing. Think T shirts that have a little room in the torso but end just below where a tummy might pooch a bit. Then add a slim cut blazer/jacket or a waisted cardigan with a hem to the middle of your bottom. If you have slender hips and a decent waist then a shorter cardigan will work.
With skirts, avoid pleats from the waist, dirndls and excessive fabric. A line with a divided pleated skirt, straight, pencil or tube all work with a more fitted elongated top. Wear heels with them because pregnant women often do not plus you'll lengthen your lower leg line.
Dresses- no underbust gathers or large tucks and nothing that doesn't follow the lines of your body. A shift style dress worn with a cardigan or other top will give you definition and shape and wearing something over it will help you feel less self conscious about any tummy pooch you may have. Button through skirts can sometimes make a stomach look bigger, especially denim button throughs which seem to pouch. Remember that a curved tummy is not unattractive to others!
Trousers- much the same as skirts. No frontal gathers. Side pockets cut on the slant can make tummies look flatter. Try different fabrics and styles especially jeans and if you find your perfect pair, buy two. Waistbands that fall slightly lower than your natural waist can help disguise a little pooch whereas high waisted trousers may emphasise it if you are short.
Good underwear is important. Don't wear over-tight lingerie. Underpants that cut into waist and buttock will make you look bigger and you don't want your bra to make the flesh around it puff out. Spanx and control pants only work if you buy them a little looser than you think you need. Otherwise flesh spills out somewhere else and you will feel trussed up too.