or 6 out of 7 bets repeatedly?
It's quite different from the method for computing losing streak.
The probability is equal to the number of losing combinations divided by the total number of combinations.
7 bets at a dice game represent 2
7 possible combinations.
the losing combinations are
LWWWWWW
WLWWWWW
WWLWWWW
WWWLWWW
WWWWLWW
WWWWWLW
WWWWWWL
It means you have 7chances on 2
7 to lose 6 times out of 7
7/2
7 = 7/128 = 5,5%