Medication lowered, flared up

Hi everyone, just wanting your opinions on my current situation. So I was cruising well on taking 6grams of Salofalk mesalazine granules daily and my doctor decided to drop it to a maintenance dose of 4.5 grams. Four or so weeks into the drop, I started flaring up again and it hasn’t gone away. I’m feeling so defeated. Mind you I’d been on the 6grams since March and was feeling so fantastic. I don’t understand why I can’t stay on 6 grams long term if it’s working for me! Doctor said Rinvoq is the next step if mesalazine fails. I really don’t want to go on Rinvoq because I want to have children in the next couple of years. What do you guys think?