Transubstantiation was what the Church defined. And they did it well before “consubstantiation” came down the pike; a point worth considering.
To take it from another angle, Christ at the Last Supper (as noted in the Gospels, and by St. Paul) did not say something to the effect of “This is bread, and I reside there too”. He said something so radical that it has come down through the centuries: This is My Body"
Read John 6 (it is better in the Greek, as the Greek is even more emphatic); Christ speaks to the group in a greater and greater emphasis of what is to come. And as note, many went away as they could not accept eating his Body. In that scene, Christ did not say that bread was contain his body, or to represent his body.
A comment made this last week or two by someone speaking about the Eucharist said also to read the story of the time between the Resurrection and the Ascension. Christ had a glorified body; it could and did do things ours can’t (with extremely limited circumstances); it bi located (the disciples going to Emmaus and the Upper Room); it passed through walls/doors (the Upper Room); it consumed food (on the shore as the apostles were fishing), and it eventually floated away upward out of sight (the Ascension). If Christ in his glorified body could do these things, why could he not change the substance (the “what it is”) of bread to his Body? Is he not truly God Incarnate?
Yes, it can be a struggle. I trust the Church as bring the Church which Christ founded, and I trust the Holy Spirit to protect it always in its seek for truth. And I trust that the Holy Spirit has guided the Church in its contemplation of the Eucharist and what that means. Scholastic Philosophy has been the underlying foundation for the contemplation of the Church on what we have been given.
And as consubstantiation came from those who broke off from the Magisterium, I would have a problem accepting that the Church got it wrong and those breaking away got it right, subsequently.
Someone you might want to consider reading is Brant Pitre in his books Jesus and the Jewish Roots of the Eucharist, and Jesus and the Last Supper (there is overlap).
One last comment: there are numerous Eucharistic Miracles. one of the subsets of consubstantiation (as I understand it) is that Christ can “leave”, resulting in bread alone. How then does one account, for example, of the miracle of Lanciano, for example?
My answer is that at the consecration, the bread and wine were changed in substance to flesh and blood, and the form of them (bread and wine) were changed for the monk who was struggling with the issue (and for the faithful, since). There are other miracles, including Hosts which bleed from time to time.
To reiterate: Christ made two absolutely astounding statements. He said “I AM” - he claimed for himself the name given to Moses by the voice at the burning bush; and he said “This is My Body” and “This is My Blood”. He did not equivocate, or talk around it. Bold, bold statements.
Welcome home! Becoming a Catholic is not a one time event; it is a life-long journey - bumps in the road and all.
It is worth contemplating.