If your caloric intake is the same, then it could be 1 or 3 things.
1. Increase salt intake causing water retention.
2. Hormonal changes causing fluid retention.
3. Increase muscle muscle mass weighing more than fat mass.
Based on your entry, I think it's most likely #3. Don't be discouraged, because after gaining muscle increases metabolism and the fat will burn away, causing further weight loss and most of all, improved physique. Just stay the course and find joy in the journey.