Identify 2 or 3 Conescutives in a string of data

=IF(E3=E2,"",COUNTIF(INDEX(E$1:$E1,MATCH(9.99999999E+307,$F$1:$F1)):E2,E2))

The problem I am having is that this formula does what it was intended, I wanted to do a count to see all the consecutive occurrences of A and B. I.E. how many times did A show up 5 conesecutive times, or B 8 consecutive etc. I am able to pull 2 and 3 out of this formula, as A and B do occur 2 and 3 times in a row, but I also need to account where they occurred 2 or 3 times and it turned into a longer string. Make sense?