The present continuous or present progressive tense is used to describe what is happening now.
This tense is formed by using part of the verb Estar plus the present participle. The present participles of IR Stem Changing verbs are irregular.
There are three patterns for stem changing verbs in the Present Tense.
O – UE
E – IE
E – I
In Present Continuous these changes are different and the change goes to only one letter.