I just now started putting on weight and I'm 24+3 weeks. I was very small to start with only weighing 106 went down to 103 now I'm 113!! My midwife hasn't been to concerned tho!! Honestly eat when your hungry your body will tell you when to eat and so will baby. Some woman put weight on differently. Just make sure your getting everything you need like veggies and protein and taking your vitamin. You could be like me and it takes awhile to put on weight but now that I'm gaining its a pound a week.
I lost 15 pounds, but now I have put a couple back on.everything I do put some back on I lose it again. It's a battle to gain weight and I am 20 w tomorrow. When I have been doing is trying to eat what I can. It still get in some sort of excercise. All you can do is try your best to eat right and be healthy. My doctor also out me on a fatty, starchy, salty food diet. That may help as well.