Psych doesn’t believe that insomnia is a side effect

Guys, I used to always sleep through the night (except for maybe 1-2 nights during my cycle when I feel extra warm). I go to bed at the same time every evening, I feel tired and I fall asleep after reading a couple of pages of my book.

Then I wake up at 2 a.m. and struggle to go back to sleep. It’s been like this since I started the meds 3 weeks ago (20 mg at first, 30 mg for the last 10 days ish).

My psych doesn’t believe the insomnia is caused by the meds because I initially feel tired and manage to fall asleep? I thought this was an established side effect? What’s your experience?