Weight gain is a stupid thing to measure in pegnancy, unless you put ona huge amount in a small time then you're fine. As for overweight... pfwah! In a few months you'll be on the best weight-loss programme ever, it's called birth and you'll lose 5kg in about a minute, plus more a few hours around the big event (with waters breaking and placenta loss).

1kg a week is fine! I went through a stage of doing that (but no weight gain inT1) and didn't do me any harm.