I am 19 and need to tighten up all areas.I have lost a lot of weight.
what can be done about loose sagging skin around belly and back and
every where? NO SURGERY and no selling of skin creams.

Same questions are asked here, but the answers given do not meet your
criteria completely:

Sagging skin after weight loss?
http://www.geocities.com/healthyadvice/Diets-Q15.html

WebMD - Staying Toned After Weight Loss
http://my.webmd.com/question_and_answer/article/1676.56277

"How much your skin will tighten depends on your age, length of time
the skin was stretched and how much it was stretched, how much weight
you lost (and to some degree how fast you lost it), the amount of
elastin in your skin, and genetics (you have no control over that).
Exercise can help as it will tighten the skin to some degree, plus it
will tighten and tone muscles under the skin, which can have an affect
on the appearance of your skin. We generally ask people to wait 8-12
months (assuming they are eating healthy and regularly exercising)
once they've reached a goal weight to see how much the skin tightens.
If after this time the skin is unacceptably loose (cosmetically
unappealing or a health risk), then surgery may need to be considered
to correct it. In some of these cases, when it is deemed a health
risk, insurance may cover the surgery."