What to do?what to do...

itching

I finally got the motivation that I was lacking and I have had good focus on food and have been exercising about 4 times a week,and have been going longer then before and making it 40-45 mins. It has been 3 weeks since I have gotten serious about it and actually doing something! But when I weigh in its so disapointing to see that after 3 weeks I put on a kilo and have only lost 400gs! I am about 5ft4 and 268 pond,I thought the bigger you are the easier the weight came off??? I do have P.C.O.S and know it can be harder for losing weight.A few months ago I went through the same deal of being motivated and trying only to lose a little and I gave up in the end and now I feel like giving up for good I just dont know what to do anymore.