Weight loss

I have two kids that just turned 1 and 2. Since having my baby last year I have lost about 30 pounds. At first I was actively trying to lose weight with a strict weight loss program for about 2 months and for the past 6 months I haven’t really been “trying” to lose and I still lost another 15 pounds..but I do chase 2 toddlers around all day...I am not sure if this is ok...when should I go to a doctor for unexplained weight loss? Without really trying I would say I lost about 15 pounds