I have had pressure on the roof of my mouth for about three weeks now, started just over my front 4 teeth now the whole roof of my mouth.

Sinus infection: Sinus infection can refer pain to teeth gums and roof of mourh. See physicain examination and likely antibiotics.

Get an examination: Your problem may be sinus or dental related. Start with your dentist for an examination and xrays if necessary. If they rule out dental issues then see an ENT for possible ct scan and futher testing.