Its not what I think is true it is actually true.
I quoted this in the other thread on this topic.
Below is a response from Father Serpa of Catholic Answers from some time ago. I have bolded the particular relevant part.
"In the first place a Catholic has no business attending Protestant church services even occasionally. To participate in a heretical worship service and especially a communion service can be sinful for a Catholic because such an act is an affirmation of what we believe to be untrue.
To attend an ecumenical service or a wedding or baptism is allowed, but Catholics are not allowed to attend such churches for the main reason of worship.
Now if there are no Catholic churches in the vicinity on a Sunday, Catholics are allowed to participate in the Liturgy of Churches whose clergy are validly ordained such as the Eastern Orthodox Churches—including the reception of the Eucharist.
Although we consider them to be in schism (not in union with the Pope) with the Catholic Church, such Churches are not heretical and share our basic beliefs.
Fr. Vincent Serpa, O.P."
I may not know better than you but I think a priest does.