Sertraline - felt great on Week 8 - now a bit 'meh'. Please tell me that wasn't a one-off!

I've been taking Sertraline 150mg for panic disorder for just over nine weeks (yesterday), gradually upped from 50mg to 100mg to 150mg. I take this alongside 15mg Mirtazapine in the morning and at night. Initially, I seemed to be making good progress and each week there would be a sign that things were improving - eg, something would happen that I would normally spin out over, instead I remained relatively calm. Then, I’d just passed the seven-week mark when I left the house on my own for the first time in four months (before that I couldn’t be at home or outside on my own), used public transport and, the biggest thing of all, attended a wedding - and danced! I couldn’t believe it. All from a few pills! However, while the Monday and Tuesday of the following week were really good, that was also my first week back at work (albeit working from home) and the week of my med review; I could see my meds dwindling and, yep, you’ve guessed it, I panicked! I subsequently got my meds, so you’d think panic over - but on the Friday I then started feeling really down. And now I’m not convinced anything is working and that ‘magic’ week was just a one-off. Has anyone else experienced similar?