One thing I've learned is every lb of muscle you gain you will actually burn 70-75 more calories per day. I changed my diet/workout routine up and so far I'm seriously seeing the benefits. I've been stuck around 185 lbs now for several months doing strictly cardio. But I've recently took up weight lifting as well and I've already noticed the difference. Just remember muscle burns fat and it weighs more than fat.
It could either be water weight or you could just be gaining muscle. Try googling on how to get rid of water weight. Hope I helped!! If you have anymore questions just ask!!