When this happens to me I take a look at the foods I ate, I don't know if you track your food. I don't use the tracker here as I find it too fiddly so I use a journal and record everything I eat as I eat it. Mine is small enough to carry with me in my bag. That way I can see what I had during the day.
Sometimes I eat more than I think when I look back and can see where the extra calories are.
I only weigh myself once a week. Don't forget at certain times you may retain water so this will make a difference as well.
I don't know if this helps and I am sure others will reply as well with more tips for you.
What ever you do Dont Give Up
it takes time to figure out what is best for you but you will get there.