No; it's a grammatical thing called "mutation" where the first letter of a word can change in certain grammatical environments, such as from d to dd (this particular change is "soft mutation").
So depending on the grammatical surrounding, it either must be d or it must be dd. (Or it must be something else such as n, with nasal mutation.)
Many countries have Welsh societies. Perhaps if you went to your local public library, they could find out if there is a Welsh language group or a Welsh cultural association near you or allow you to put up a card on their notice board appealing for other Welsh learners to join you.
Britain has a Welsh language TV channel called S4C. Check out their website. S4C has one of Britain's longest running soap operas, which is called "Pobl Y Cwm". Another program you will enjoy is "Noson Llawen". It is an evening of folk songs, dancing, comedy, poetry, etcetera.
I live in Carmarthen, which is not the biggest city in Wales. It is not even the biggest town in this county, but S4C is building its new headquarters here because it is one of the Welshest towns in Wales. I hope you will visit us. You will see road signs and shop signs in Welsh. You will find many people who can speak Welsh and they are really nice. They are willing to help people trying to speak their language. If you do not know the Welsh word for anything, use the English. That is what most Welsh people do.