Your or another team's winning streak can be found on the team's main page. It is not known if a winning streak contributes to Overconfidence in a game. Only competitive matches (League and Cup) contribute to your winning streak. Friendlies do not affect it.
An example of a winning streak is this: The team is undefeated for 6 competitive games and has 5 consecutive wins.
If in the next three competetive games the above team were to draw and win the other two, the message would say: The team is undefeated for 9 competitive games and has 2 consecutive wins.