Normal weight for a fit/healthy 5'3 person?

No I had a child 2 YEARS ago. I was 106 2 months ago and now 111. I'm just trying to figure out why I am going up like that. Seems a little extreme of a jump especially since I haven't increased my calorie intake.

I'd bet money on it being water. Your muscles hold onto water for repair. It has nothing to do with calories. You should take measurements so you don't freak out over the scale so much.

That personal trainer sounds really confused. If you listen to him, you're going to be really confused. Keep in mind they go through a short training course, they don't even have to have completed college. Some of them really know their subject and others are clueless. You'd probably be better off doing your own research than listening to this guy.

If I were you I would focus on upping the intensity of training and setting personal fitness goals, like how much you can lift, how fast you can run, etc, rather than worrying about the scale. Increasing your level of fitness is going to eventually help flatten and tighten your stomach.

I'm currently 5'3 and 111 lbs. Before having my first daughter I was 98 lbs (under weight I know)...

I have no idea whether that was underweight. I'm 5'2" and I was 90 or in the low 90s for years. That was perfectly normal for me. I'm now around 100 because I'm older and more sedentary.

People come in a wide variety of builds and their body composition is not identical. You have to start thinking for yourself about what is healthy and desirable and practical (and of course consistent with any examinations or test results you receive from medical professionals and your own weight history).

Some other comments:

What is your body fat percentage?

I think it's odd that your PT is assessing you by BMI, that's a crude tool used to indicate whether populations are overweight or obese, which you clearly or not. At the level of the individual, the BMI, is not very telling. At times I'm classified as underweight, which I'm not. In addition, there's a new BMI formula that yields different results. Under that I'm normal.

Not every woman who's had a baby can have a perfectly flat stomach. I'm not saying that's the case for you, but you should consider it.

Not every woman has firm arms. it's genetic. What do the older women in your family look like? If it's not genetic and you don't have a huge amount of fat in your arms or are gradually reducing it, are you doing the right exercises to firm your arms, especially triceps exercises?

One normally doesn't think of strength training in terms of time. Rather one talks of exercises and sets and reps and weights.

Are you doing interval training? That might help with fat loss.

Are you following a diet that is supposed to encourage fat loss?

I would consider all of the above in developing a program that works for you. But you're lucky, because even at your current weight you are well within in the normal range. You just need to find the right combination.

it didn't make sense to me why he would say to be below but he tried to explain it as wanting to have no body fat you would be less then the BMI to be thin and toned. I don't know. Whole thing confuses me! I'm just weirded out by gaining weight. I have NEVER weighed that much. I can't explain it. I just want my stomach to be flat. That is all I want. I want it to be flat and tight.

NO body fat?????