Ads for ... ? I don't think it's the texting app, as I use that and am not hampered by ads. It may be a free game or other app you've added recently if they've just started appearing. Free apps are free, but some come with ads that go away when you buy the full version.
It may be hard to determine which app, but I would start with any free games or free apps you may have downloaded recently, disable those and re-enable one ata time until you find the culprit.