I noticed a small lump under my tongue, behind my front teeth that seems to be at the bottom of my gums. it's painless and moveable. it hasn't grown. ?

Gum growth: Can be a number of things. Most probably a salivery gland issue. You should see an oral surgeon for an evaluation.

Normal: If at base of bone behind front teeth then it is the bony attachment point for your muscles under the tongue and the floor of the mouth. If it is in the midline and coming down from under the tongue when you raise it , then they (usually 2) are your sublingual salivary glands. Normal. Good Luck

Suspicious lump?: Regardless the cause... I would advise you to have the lump under the tongue examined by a dentist or dental specialist (e.g. oral surgeon, OFP). Any suspicious lump that does not resolve itself in 2-3 weeks should be evaluated.