Period Length

So I’ve always been really regular with my period coming at the same time each month and lasting about 5 days. But recently I’ve gotten my period twice in one and month, and now I’ve had it since the 7th of July. So I’ve had it for almost 20 days and it’s totally not normal for me. The only thing that’s changed in my regime is I started taking Prozac about a month ago. Does anyone know if Prozac can cause excessively long periods, or has anyone else experienced this as well while taking Prozac or just experienced it in general? Any advice on what I should do?