I'm 5'9 also. Was 97kgs before falling pregnant, then i was 92kgs at my 6 week appt.

I have weighed myself since, i wont be weighed until my first antenatal appt on the 25th. But i reckon ive lost another couple of kilos. I have had the worst morning sickness, i occasionally still get it. The past week i haven't been able to keep much done. Id like to aim to not gain more than 100kgs but wont stress if i do.