It would really help if you could post a video of yourself playing..
Should I assume you have tried playing other trumpets with the same result.. just to rule out mechanical issues with your instrument?
Now some guessing.. because I haven't seen or heard you play yet ( I hope we do)
If you are putting too much lip inside your mouthpiece.. you will get a pinched tone and it won't matter what size mp you have because you will just defeat the purpose of a wider cup and stuff more lip inside.. IT also may be coincidence by every player I have known to have this tone issue has their lower jaw way forward .. that is just a personal observation.. lots of great players have their lower jaw forward so I am not saying that is bad .. but it might be applicable.
Cat Anderson played with his teeth almost together ( so I have read) but I can't .. if I try I get a pinched tone ... something to think about? maybe...maybe not.
One of our Moderators here teaches the circle of breathing (?) ... inhale.. exhale.. inhale..play ... it really is effective .. and even if it doesn't help your tone it will help your playing.
I would also look to see where the ring around my lips is left from the mp ...my guess is that you have an awful lot of "white" .. if you try to get the ring close but not on the "red" part of your lips it will force you to open up a bit ... that being said .. when you do.. if you do .. your range will probably go south until you strengthen your breath support.
Most of all .. find a good long tone warm up and as just about everyone here said .. listen .. you can feel the horn light up when you get full resonance ... at that point you will have reach full consciousness and the gods will smile upon you.
seriously.. post a quick vid