Foondoon,
You have found something the diaper ads never tell you - that soggy diaper sag and need support!
You did not say which tabbed diaper you are wearing. Disposable tabbed diapers with a cloth-like outer shell are notorious for stretching. Diapers with all-plastic shells stretch some, but much less.
Depending on how much support you need, your primary options are spandex-type underwear, compression pants, onesies, or diaper suspenders. In warm weather sports-activity shorts with a built in mesh liner will work.
I wear either a onesie or compression pants with ConfiDry Dry 24/7 diapers with a booster and, like mlhjr, sometimes both.
--John