I if you go up a whole reed size (a.k.a size 3 to 4) and you can`t play on the higher reed number, does that mean you need to build a stronger embrochure because the reed is thicker?

I had to build up to the harder reed size. I had to start on a 2 1/2 and am now on 3. i play bari sax. you probably have to get used to the new size. you might need to build just a little bit a stronger emboture, since it is a thicker reed. if you still can`t get it, then try a 3 1/2 reed.