Hi MegnB - I know exactly where you're coming from! The Utro does that to me too, in fact most prog does, can't even make 12 days, 7 at the very most and I've also requested a hysto as I just can't take any more.
I really do empathise but I imagine the Utro, in your case has just triggered a bleed you would've had on the generic prog, just because you needed a bleed. Oral progesterone has lower absorption and a less powerful effect on the endo as it's broken down by gut and liver. It may be that using it vaginally (either product) has set off a bleed because your oral intake wasn't enough.
Your doc may suggest an increase of oral dose to 200 or you could try vaginally at 100 if that suits your lifestyle. It might also be a jumping off point for Utro and time to try another prog? You can chat about that with your doc when you're there.