What could cause lower legs to swell and ankles and feet? all tests came back normal and ecg normal. my legs and feet have been swollen for couple weeks now?

For bilateral leg edema, the most common causes will be kidney, heart or liver diseases. I knew one young lady who had rheumatoid arthritis and leg edema was the first symptom which is quite rare. Venous insufficiency can cause leg edema but rarely symmetrically bilateral. Cyclic edema can occur with menstrual cycle but it is rare to happen just now at your age and cyclic edema is not persistent.

I agree with Dr. Le's answer, but make sure you get a urinalysis to determine if you're losing significant amounts of protein in your urine. I've seen several cases of this despite normal blood tests of kidney function( BUN,CREATININE, eGFR). This can occur with glomerular damage seen in diseases like myeloma,amyloidosis, diabetic&hypertensive nephropathy before kidney blood tests turn abnormal