Is it difficult to believe that Jesus is really present in the Eucharist?
Yes!
Why do you think that Christ hides His Real Presence under the appearances of bread and wine?
First of all, even though it is hard for us to believe, Jesus is very clear that He truly gives us His Body to eat and His Blood to drink.
Not being able to see Jesus in the Eucharist is actually a gift, because it exercises and grows our faith, our deep trust in God. Without seeing God directly, when we trust Him anyways because the evidence all around us (the phenomenal order of creation, the goodness of truth and beauty, the power of love, etc.), we actually become more capable of loving and, therefore, of experiencing joy! “Blessed (happy) are those who have not seen and have believed.” -Lk 20:29 So, literally, the greater our belief, the happier we will be!
Also, since God is so good, He gives us His Son under the appearances of bread and wine, so that it is easier for us to receive the gift of the Eucharist and eat it without being shocked or offended.