Struggling to lose weight.

I weighed myself upon waking and was so happy to find that I had gone down four lbs, but stupidly weighed myself again a couple of hours later to see if I had stayed the same, and I’m back up three lbs. How am I meant to lose weight if I can’t keep the pounds off? I’m eating good and exercising, I don’t know what to do. I have under a year to lose over three stone and I am really struggling with it all. When should I be weighing myself ideally to avoid disappointment?