Dear Arlene:

No. It is impossible to legitimately belong to two religions. Christianity is not compatible with any other religion. A Christian must be exclusively a Christian. Since there are differences between Catholics and Protestants, a Catholic cannot be both Catholic and Protestant. A Catholic must be exclusively Catholic.

As for Wicca, which is witchcraft, God condemns this religion outright. God calls it an "abomination":

(Deuteronomy 18:9-12)  "When you come into the land which the LORD your God gives you, you shall not learn to follow the abominable practices of those nations. There shall not be found among you any one who burns his son or his daughter as an offering, any one who practices divination, a soothsayer, or an augur, or a sorcerer [witchcraft], or a charmer, or a medium, or a wizard, or a necromancer. For whoever does these things is an abomination to the LORD; and because of these abominable practices the LORD your God is driving them out before you. 

Witchcraft is one of the worse sins one can commit because it is a sin against the First Commandment to worship no other Gods but the True God of Abraham, Isaac, and Jacob (the lineage to which came Christ as the Son of God).

The god of Wicca is Satan himself even though most Wiccans may not know that. Those in the upper hierarchy of Wicca will tell you that the god of Wicca is the horned god Lucifer. But, worship of any god other than the True God is worship the devil at least indirectly.

Any Catholic out there with the delusion that they can be Catholic and Wicca needs to renounce Wicca completely and totally, destroy all books and paraphernalia of the craft, confess the sin in the Sacrament of Confession, and have nothing more to do with Wicca in any fashion whatsoever. This includes severing friendships with all Wicca people and organizations.  

Failure to be exclusively Catholic (exclusive Christian) runs the risk of one's soul going to hell.

God Bless,
Bro. Ignatius Mary