Gained almost 40 lbs in a year

So when I had my daughter I was overweight 205 before getting pregnant 232 while pregnant and then I went down to 190 two weeks after she was born. I breastfed for five months didn’t change anything I did if anything I do more now chasing a one year old around and cleaning every single day. I don’t eat junk food or eat out much i went to my doctors 2 days ago and am now 230 since January of last year my doctor doesn’t understand why and I even moved a whole house by myself basically in August besides the really heavy furniture up the steps I’ve been using whole wheat everything and talking 4 mile walks as weather permits going to the gym but just can’t seem to lose any weight even with only drinking water diet pills ext it’s driving me insane up until a few month before I got pregnant I was always 150 and below and I’m only 5’4 and I’m literally hating the way I look more and more everyday. And I don’t know what to do my doctor tested my tsh levels and they care back 3.8 outta 4.2 being the highest their standard range. Anyone know what the cause could be