Minny - are you still peri meno? I am assuming you are, so your own hormones will be fluctuating and dropping so I believe this will have an effect on any withdrawal bleed until the HRT takes control.
You can take Utrogestan in two different ways - the leaflet isn't very helpful about this. 100mg for 12 days is not the standard dose, it is meant to be 200mg for 12 days if used on a sequential basis as you are. However, if one is using a low dose of oestrogen then 100mg for 12 days may be sufficient. The regime of 25 days our of 28 is considered the continuous version for women in post meno although some women in late peri meno can get away with using it this way and may well get some bleeding after the break. When first starting any regime there may be little or no withdrawal bleed and perhaps this is what has happened to you - erratic spotting and bleeding is also common. A small promotion of women get little or no bleed on any sequential HRT whilst others may get a heavy bleed - we are all different. The PMT you are feeling will be due to the withdrawal of the Utrogestan and this is common on any HRT type.
It often takes 3-6 months for the body to adjust to any HRT so I would just stick with what you are doing and give it more time. You may find you get a more substantial bleed next time.
As long as you are getting some relief from flushes and night sweats and generally starting to feel better, then this is good. DG x