Hi Since Yesterday My Left Knee Has Pain When I

Hi since yesterday my left knee has pain when I go upstairs or come downstairs, we have many stairs at home and I have a 2 years old about 26 pounds which I carry most of the time plus heavy bags and her stuff with me and her when I come to home. My mom had knee replacement surgery couple years ago and I am worried I might have to do the same what shoud I do should I see a doctor for X-ray or MRI ?