Weight insecurities

Hi, so I’m 18 weeks pregnant, haven’t gained any weight yet, maybe a couple of lbs, just eating how I normally would. Before getting pregnant I had lost about 2st in two years, I’m just under 5ft so putting weight on always looks worse on me and is very obvious, and I recently was shown a picture of how I use to look - I know this sounds ridiculous, but I’m now worried about piling weight on after seeing that photo. I know I can lose this extra weight when baby is here and I really want to try and enjoy being pregnant, tho, I don’t how a bump yet - just look like I’ve eaten a big meal 😂 so does anyone have any tips on how I can change my mind set surrounding this - be more positive etc? And what safe exercises can I do while pregnant to maybe make me feel more secure and happy? Thanks ladies 😘