I want to come off sertraline, but they increased it

I m43 went to my doctor today to discuss my low mood and other side effects and if sertraline was still right for me (I also get a wierd withdrawal symptom if I miss one) Im currently on 150mg a day and they upped it to 200mg, I don't want to be on this high amount and I don't think an extra 50mg (200mg is max)is going to help in the long term, I felt better for 6 months when I went from 100 to 150! So I feel like it's a temporary fix. She said they can look at an alternative if this increase doesn't see results after 8 weeks. Im going to make another appointment tomorrow and try and see the doc that put on sertraline first time round.

I don't want to go in all "I want a second opinion" but I do want to be firm, but why is she so sure that another 50mg will fix it(me), how should I approach this?