Sudden and Serious Bloating

so I have been intermittent fasting for about 2-3 weeks, and doing so has caused me to lose weight. However, the past couple of days - I have noticed that my stomach/belly has been getting larger. As of today, it is larger than what it was before I lost weight. In addition, it’s very firm - it is not loose fat like it was previously but instead it is firm and hard to the touch. The only exercise I’ve started to do was biking for 20-30 minutes every evening for about two weeks. I’ve already had my period this cycle and am due for my next one in two weeks, so this definitely isn’t just my usual bloating that I have around my period. What could this be? Am I really just gaining weight or is there another issue it could be?