I feel so insecure PLEASE HELP

Try to work on your abdominal muscles. One of the reasons they sag is because of week muscles in that area. The more muscle you build and tone it up, the better that area will work. Don't be harsh on your self, it just requires some discipline with food but mostly an exercise routine you can stick to for at least the next 6 months. You got this girl

It's just normal abdominal fat. The issue is that it's dropped and the skin is stretched. The only way to full resolve this is to have a tummy tuck. You can most certainly tone up a bit, lose weight naturally and make it better....but resolution can only come in surgical form.

Be really kind to that skin too, moisturize well and try to eat good healthy fats and oils like those in salmon and avacado etc. to help the skin regain some elasticity. Palmers makes an oil that is really good for this sort of thing.