mirtazapine insomnia advice please

After two weeks of no sleep doc gave me mirtazapine 15mg. Night 1 out like a light felt rubbish next day. Day 2 slept well felt better in day. night three slept fitfully fine in day. Last night could not get to sleep same old thing kept hearing things just as I dozed off or intrusive thoughts waking me almost felt like I was on play drifting off and some suddenly pressed rewind . This went on all night. Is it usual for sleep to be hit an miss? Or do I need to try higher lower dose. My insomnia causes me aniexty not they other way round. All advice appreciated please I was so grateful to be sleeping again feel devastated now .

I've had a couple of nights where I've not been able to sleep with it and it made me worry it wasn't working. Stick with it :hugs: hope you get some sleep tonight.

Thanks wnsos that's reassured me somewhat.☺