I have been on Sertraline now for 16 weeks for severe anxiety and panic disorder. I did 1 week on 25mg, 5 weeks on 50mg, 6 weeks on 75 mg and 4 weeks on 100mg. The first 6-7 weeks I felt awful, heightened anxiety and insomnia, then I started on 75mg and felt amazing. Got my energy back, was sleeping well and felt like the old me again, although I was still getting occasional anxiety, so decided to go up to 100mg. Since then I have severe insomnia, feel irritable, have no energy and def not feeling as happy. Also waking up with anxiety in my belly again. Should I go back down to 75mg? I would have thought that after 4 weeks on 100mg I would have seen an improvement.