Advice on Weightloss during pregnancy??

need everyones advice/thoughts - I had planned to sort my body out before I was pregnant as I had really let myself go but then obv baby came along and that got put on hold ... I still feel horrible but not cause of bump just my face my arms my legs I was wondering instead of going on a diet and reducing my intake of food I could just eat healthy meals and cut out all the shite basically.... I want to use my arm weights ( they aren't heavy just enough to make them a bit sore after a workout) and I want to go walking and swimming but i've seen so many posts that losing weight is bad during pregnancy... I am chunky and my BMI is 35!!!!!!!! I have a karate background so I am hoping most of that is all the muscle lol but i have got some flab on my belly i am just scared for my child and putting strain on my body.. all advice/suggestions/experiences welcome!!!