I lost count and had to start again.

我数着数着忘了，不得不又从头开始数。

《牛津词典》

I don't know, I lost count.

我不知道，我数不过来。

youdao

This was probably the 150th blade, but I must admit I lost count.

完成的这个差不多是第150枚刀片，但我得承认还有很多我都忘了数。

youdao

Watching the financial media early in the day on Tuesday, I lost count of how many middle-aged money managers were scolding Zuckerberg in abstentia and in advance with hoodie jokes and the ever-present, unfavorable comparisons to the formative years of Amazon.com (NASDAQ: AMZN) and Google (NASDAQ: GOOG).

FORBES: Zuckerberg: Facebook Will Make the Social Mobile

He can go past people with power and pace, but I've lost count of the number of times I've looked up and seen him stuck on the halfway line.

BBC: SPORT | Football | My Club | Liverpool | Houllier faces mounting pressure

I've lost count of how many retired numbers line Yankee Stadium's left field wall.

FORBES: Where It's All About The Game