I can understand what u r feeling as i weighed about 84kg when i found out i was pregnant a few weeks ago so i was also worried about putting on to much.I'd actually got down to about 72 kg earlier in the year but had put it back on over winter.When i went back to the docs though i weighed 82.4 kg so i'd actually lost weight,i couldn't believe it!
I've just had to tell myself to not worry too much try to eat healthy & do some exercise & if i put on too much,oh well i'll just have to work harder later on.
I'm really trying to eat well & not have too much chocolate or junk food.
I think it helps that sometimes i feel too ill & can only manage some soup & an apple
Just try ur best,don't obsess over it other wise u will just stress urself out too much.
Walking is good,& maybe u could find some water aerobics classes or something like that as they r low impact.I think they have special classes for pregnant woman too