Congratulations on the new bub.
I can really feel where your coming from. I was able to exercise during my 1st pregnancies (was a regular gym goer 3-4 times a week) BUT I sill piled on 16kilos even though I was exercising til 37 weeks. Unfortunately it wasnt fluid retention & I only lost 4 kilos in hospital leaving me 12kg to lose.
I think hormones play a big part in weight loss(or lack of) after pregnancy. For some it seems like the fat melts away but for the majority I think most have to actually put some plan into action to actually lose it & reality is many dont. They do say it takes 9months for your body to go back to normal the same length of time it took to get to final stages of full term pregnancy. By normal I dont mean weight wise(because sometimes that doesnt happen) I mean your hormone levels, your uterus, your breasts, your muscles & ligaments which losen up during the pregnancy. So you are doing very well to actually be thinking /wanting to do something about it & only 6 weeks post baby.
I would suggest you take it easy over the next few months enjoy your baby & the special time you now have together, as your body recovers from the last 9 months you will start to lose some weight. Dont rush things.
Both my pregnacies & post birth were very different. 1st time I exercised & put on 16kg then went to the gym after 5 months & it took me 6 months to lose 4 kilos that I had left to lose. 2nd time around I couldnt exercise put on 18+ kilos & post baby I didnt have the time to exercise with a baby & a toddler at home plus cold weather. But i started on a meal replacement program & was able to lose 7kilos in 10-12 weeks. Exercise can help but is not an integal part of weight loss journey and it certainly didnt help me much during or after my pregnancies.
I wish you all the best with the new baby & the weight loss. Send me a personal message if you have any queries.