It would be good to have renal bloodwork that includes your GFR (glomerular filtration rate) and albumin and creatinine levels. MGUS can sometimes smack one's kidneys around. I've had IgA Kappa MGUS for 8 years, and this year chronic kidney disease showed up; my only other risk factors are being 70 and having celiac disease. Bubbly and protein bits in urine suggests one's kidneys are not filtering proteins as efficiently as they should. Urinary tract infections commonly have different symptoms (itchy, smelly,...).